Performance Sodium-ion Batteries Research Articles

Exploration of PVP-Combustion Synthesis and Electrochemical Performance of O3-type NaxNi0.33Fe0.33Mn0.33O2 Layered Material for Sodium-Ion Batteries

The performance of sodium-ion batteries critically depends on the cathode materials used, making it essential to explore and optimize suitable candidates. Among them, O3-structured NaNi0.33Fe0.33Mn0.33O2 has emerged as one of the most promising cathode materials due to its outstanding electrochemical properties. However, there still exists a knowledge gap regarding the detailed synthesis conditions and the comprehensive performance of the full cell using this material. In this study, we investigated the influence of synthesis temperature, time, and sodium content on the electrochemical performance and charge-discharge kinetics of O3-structured NaNi0.33Fe0.33Mn0.33O2, prepared via the PVP-gel combustion method. Through systematic analysis, we elucidated the impact of these synthesis parameters on the material’s properties and battery performance. The results revealed that the optimized conditions led to a cathode material with superior electrochemical performance, exhibiting enhanced capacity with 139 mAh g−1 at 0.1 C and 96 mAh g−1 at 10 C. Additionally, a full cell using the optimized cathode material was studied, showing promising performance. This research sheds light on the significance of synthesis parameters in tailoring the electrochemical properties of O3-structured NaNi0.33Fe0.33Mn0.33O2 for sodium-ion batteries. The insights gained from this study hold valuable implications for the further development of practical sodium-ion battery cathode materials.

Bio-inspired design of a self-supported bismuth microforest for high performance sodium storage

A self-supported bismuth microforest anode material, prepared by a simple, efficient and scalable in situ galvanic replacement approach, exhibits high performance for sodium-ion batteries.

Surface Modification of NaCrO2 Positive Electrode Material for Sodium-Ion-Batteries

Sodium-ion batteries are potential successors of lithium-ion batteries, due to the abundance of sodium resources, which leads to up to 30% cost reduction when the two systems are compared directly[1]. While the cost advantage is high the performance of sodium ion batteries still needs improvement if they are to replace their lithium counterparts in many areas. Stability and performance are big areas which need to be improved.The volatile (H2AlOtBu)2-precursor can be used to create a coating of HAlO on metal surfaces at 270°C from the gas phase via chemical vapor deposition. It has also been used to coat Li1+x(Ni0.85Co0.10Mn0.05)1-x positive electrode material for lithium ion batteries in an autoclave at 180°C, resulting in a LiAlO2 layer and improving cycling stability.[2],[3]In this work the same coating procedure was applied to the NaCrO2 positive electrode material resulting in a similar coating and improving the performance of the material in electrochemical tests in half cells. The coating received has been shown to be a mix of different aluminium compounds resulting in an artificial cathode electrolyte interface. Electrochemical testing shows that the capacity of the treated material is higher than the capacity of the pristine one from the first cycle and it shows increased cycling stability. These improvements can be attributed to a lower resistance of the coated compared to the pristine material as shown by electrochemical impedance spectroscopy.Overall the coating procedure is simple and the required amount of 0.3 weight percent of precursor material compared to the positive electrode material is very small for a big effect on electrochemical performance.[1] D.Larcher, J-M. Tarascon, Nat. Chem, 2014, 7, 19-25[2] M. Veith, S. Faber, H. Wolfanger, V. Huch, Chem. Ber. 1996, 129, 381.[3] A. Martens, C. Bolli, A. Hoffmann, C. Erk, T. Ludwig, M. El Kazzi, U. Bredde-mann, P. Novák, I. Krossing, J. Electrochem. Soc. 2020, 167, 70510.

Heteroatom-Doped Carbon-Shelled Iron Phosphide Microcuboids as Freestanding Negative Electrodes for Long Cycling Sodium-Ion Batteries

Energy storage devices (ESDs) have become indispensable for maximum renewable energy penetration and progress towards the elimination of fossil fuels in electricity generation. Also, high-performance ESDs are urgently needed for wearable and flexible devices, electric vehicles, and internet of things (IOT) applications. Lithium-ion batteries (LIBs) presently occupy the largest share of the EES market, however the cost-per watt stored is too high and the finite supply of Li means that they cannot offer a long-term solution to the world’s energy challenge. On the other hand, sodium-ion batteries (SIBs) are regarded as complementary ESDs and potential replacements for LIBs due to their relatively lower cost, abundance, and uniform global distribution of Na.[1] Furthermore, SIBs can operate in a wide temperature range and inert with Al, benefiting the construction of low cost and safe ESDs. Nonetheless, the performance of SIBs is limited by sluggish diffusion of Na+ in Na-insertion materials owing to large size of Na+ (1.02 Å).[2]The major challenge to developing SIBs is the lack of suitable electrode materials capable of efficiently accommodating Na+. SIBs are rocking-chair cells like LIBs, however, Na-ion storage in traditional graphite is extremely poor (< 35 mAh g-1) due to insufficient interlayer spacing.[3] Phosphorous presents the highest theoretical capacity (2596 mAh g-1) for a SIB anode, however, it suffers from poor cycling and large volume expansion (490 %) during sodiation/desodiation.[4,5] Low cost and environmentally benign iron phosphides present slightly better volume expansion and a theoretical capacity of 926 mAh g-1, but its charge storage mechanism is unclear.[6] The lack of suitable SIB anode with high capacity and long cycle life remains a major hurdle to the full-scale development of SIBs.In this work, we synthesized core-shell FeP microcuboids on freestanding carbon cloths substrate as a high capacity (< 800 mAh g-1), long-cycling anode for SIBs. The synthesized FeP microcuboids exhibit distinct physical and morphological features for efficient sodium-ion storage. It possesses a porous core within a 10 nm carbon shell, which enhances the surface area, enable fast Na+ diffusion and buffers the FeP anode against large volume variations during cycling. The integration of different heteroatoms including fluorine and nitrogen successfully improved the electronic conductivity and structural stability. Finally, using techniques such as in-situ X-ray diffraction analysis and ex-situ TEM and electroanalytical methods, we probed the conversion reaction storage mechanism and uncovered a pseudocapacitive dominated storage process. Finally, our work provides crucial insights on the rational design of high-performing metal-based phosphide anodes for alternative-ion batteries.

Advances in 2D Ultrathin Nanosheets of a2FeSiO4 (A= Li, Na, K) for Next-Generation Alkali-Ion Batteries

Although lithium-ion batteries (LIBs) have become ubiquitous in various applications, the limited resource of Li and increasing cost hinder their scalability for grid-scale energy storage applications. Thus, alternative rechargeable batteries that use more earth-abundant elements such as sodium and potassium have received significant attention. However, the distinct different properties of Li+, Na+, and K+ ions hinder the extensive development of universal host materials for alkali metal ions. Polyanion-type electrode materials, which contain polyanionic groups (XO4)n −, (XO4F)n −, and (XmO2m+1)n − (X = P, Si, S, etc.), have garnered significant interest owing to their remarkable structural stability and adjustable electrode potential; this properties make them excellent candidates as cathode materials in sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs). Among these, A2FeSiO4 (AFS) (A= Li, Na, K) is highlighted as a promising cathode material due to its abundant Fe resources, low cost, and non-toxicity. The crystal structure, transport pathways, and synthesis techniques of Li2FeSiO4 (LFS) have been extensively explored whereas research on Na2FeSiO4 (NFS) as a cathode material is still in the process of maturing and research on K2FeSiO4 (KFS) is very rare. The large ionic radius of sodium and potassium presents a significant challenge to effective ion-intercalation reactions for energy storage in electrodes, destabilizing the crystal structures of host materials. In addition, orthosilicates exhibit poor electronic conductivity, greatly limiting its practical application. To address this issue, various techniques have been explored, which include nanostructuring, coating with conductive polymers, and metal doping. In this study, a facile solvothermal technique for the fabrication of ultrathin 2D AFS nanosheets by hydrothermal transformation and propose the reaction mechanism for this chemical transformation. The as-obtained AFS nanosheets are highly exfoliated using oxalic acid as the exfoliating agent to improve their electrochemical performance. These nanosheets are designed to mitigate the diffusion limitations encountered by alkali ions when traversing the densely packed structure of AFS. The highly exfoliated AFS 2D nanosheets greatly improve the electrochemical performance and cyclability of the cathode. The nanosheets exhibit a specific discharge capacity of 149 mAh g-1 for Li+, 99 mAh g-1 for Na+, and 88 mAh g-1 for K+ when operated at a current density of 100 mA g-1. Moreover, the nanosheets display exceptional capacity retention, with a retention rate of 75% for Li+, 99% for Na+, and 65% for K+ after 100 charge/discharge cycles for each of the cathodes. This study demonstrates the potential of 2D nanosheets for stabilizing the silicate-based cathode materials against structural and volume changes, and for improving their electrochemical performance in SIBs and KIBs. Figure 1

Transport Properties of Hard Carbons

Sodium-ion batteries (SIB) have been heavily researched, as a potential replacement for Lithium ion batteries (LIB) as their components are more readily obtainable, lower cost and they have similar working principles to LIB. Hard Carbon (HC) is the current state-of-the-art anode for SIB material due to its relatively low cost, overall performance and availability. Great effort has been focused into improving and better understanding the overall mechanism of HC, which is still a subject of debate.To better understand the mechanism of, and the obstacles to, charge transfer during charge and discharge of the cell, Hard carbon has been studied at different temperatures. The transitions between different stable and unstable phases are observed which have not been taken into consideration as of now in the literature. Exploring the thermodynamics and kinetics of the cell-system during the charge and discharge at different temperature with different methods, such as Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical impedance spectroscopy (EIS) provides much-needed insights to elucidate the limits and obstacles to ion transport, which can then be addressed. EIS is one a key tool which provides the exchange current density, a measure of the rates of electron transfer as the ions migrate between the electrolyte and the electrodes, indicating the impedance of the different components in the cell at different frequencies. This is combined with Raman to further investigate these phase changes at different temperature.The understanding gained of the limits and obstacles to charge transfer will be highly beneficial in designing better suited hard carbons to improve their overall cell performance in SIBs.

Enhanced Sodium Ion Batteries' Performance: Optimal Strategies on Electrolytes for Different Carbon-based Anodes.

Carbon-based materials have emerged as promising anodes for sodium-ion batteries (SIBs) due to the merits of cost-effectiveness and renewability. However, the unsatisfactory performance has hindered the commercialization of SIBs. During the past decades, tremendous attention has been put into enhancing the electrochemical performance of carbon-based anodes from the perspective of improving the compatibility of electrolytes and electrodes. Hence, a systematic summary of strategies for optimizing electrolytes between hard carbon, graphite, and other structural carbon anodes of SIBs is provided. The formulations and properties of electrolytes with solvents, salts, and additives added are comprehensively presented, which are closely related to the formation of solid electrolyte interface (SEI) and crucial to the sodium ion storage performance. Cost analysis of commonly used electrolytes has been provided as well. This review is anticipated to provide guidance in future rational tailoring of electrolytes with carbon-based anodes for sodium-ion batteries.

Crumpled graphene with graded interlayer spacing for high-rate Na+ storage

In electrode preparation, graphene-based electrodes usually form a uniaxially oriented stacking structure, which limits the Na+ diffusion in graphene electrodes for sodium-ion batteries (SIBs). In this work, a crumpled graphene (CG) anode with graded interlayer spacings was synthesized, and CG exhibits high-rate performance for SIBs. The CG has a folding microstructure like a paper clip that facilitates rapid adsorption/desorption of Na+ on its surface so that the diffusion kinetics of Na+ could be improved. The x-ray absorption fine structure and transmission electron microscope proved the mechanism of Na+ co-adsorption and explained the reason for its high-rate performance. When the three-dimensional CG is used as the anode of SIBs, it has a high-rate performance of 146 mAh g−1 with the current density increasing to 1 A g−1, and CG still maintained about 79 mAh g−1 after 1000 cycles at 0.5 A g−1 with good structural stability.

MXene-based anode materials for high performance sodium-ion batteries

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.

Large scale preparation of Na3V2(PO4)2F3 with cross-linked double carbon network for high energy density sodium ion batteries at −20 °C

Na3V2(PO4)2F3 (NVPF) is considered as one of the most promising cathode materials for high-voltage sodium ion batteries, because of its high energy density and rapid ion diffusion ability. Yet, the insulating nature of (PO4)3− and the perishable F− cause the NVPF suffers from poor rate performance and short cycle durability. Herein, a particular three-dimensional double carbon network-intertwined NVPF nanospheres (notated as NVPF/CNTs) are successfully prepared by spray drying method. The coting carbon on the surface of NVPF can collect electrons at same time effectively improve lattice stability. And the unique conductive three-dimensional CNTs network framework has significantly improved the electrical conductivity between particles and enlarged the contact area between the cathode and electrolyte. Thanks to the unique structure, the electrochemical properties of NVPF/CNTs electrode has been significantly improved, showing awesome rate capability (127.7 mAh g−1 at 0.1 A g−1 and 77.7 mAh g−1 at 10 A g−1) and ultra-long cycle life (92.1 % capacity reminded after 20,000 cycles at 10 A g−1). In addition, it has excellent adaptability to low temperature (96.8 mAh g−1 at 0.1 A g−1, 98 % capacity retention after 500 cycles at −20 °C) and considerable energy density of 353.4 Wh kg−1 in NVPF/CNTs||hard carbon full-cells. These excellent properties further enhance the competitiveness of NVPF/CNTs to achieve high performance of sodium-ion batteries.

Metal-injection and interface density engineering induced nickel diselenide with rapid kinetics for high-energy sodium storage

The key to the innovation of sodium-ion batteries (SIBs) is to find efficient sodium-storage electrode. Here, metal Mo doping of NiSe2 is proposed by modified electrospinning strategy followed by in situ conversion process. The Mo-NiSe2 anchoring on hollow carbon nanofibers (HCNFs) would make full use of the multi-channel HCNFs in the inner layer and the active sites of Mo-NiSe2 in the outer layer, which plays an important role in buffering the volume stress of Na+ (de)insertion and reducing the adsorption energy barrier of Na+. Innovatively, it is proposed to jointly regulate the SIBs performance of NiSe2 by both metal atom doping and interface effects, thereby adjusting the sodium ion adsorption barrier of NiSe2. The Mo-NiSe2@HCNFs exhibits remarkable performance in SIBs, demonstrating a high specific capacity of 396 mAh/g after 100 cycles at 1 A/g. Moreover, it maintains outstanding cycling stability, retaining 77.6 % of its capacity (211 mAh/g) even after 1000 cycles at 10 A/g. This comprehensive electrochemical performances are due to the structural stability and outstanding electronic conductance of the Mo-NiSe2@HCNFs, as evidenced by the diffusion analysis and ex situ charge–discharge process characterization. Furthermore, coupled with the Na3V2(PO4)2O2F cathodes, the full cell also achieves a high energy density of 123 Wh kg−1. The theoretical calculation of the hypervalent Mo doing further proves the benefit of its Na+ adsorption and denser conduction band distribution. This study provides a reference for the construction of transition metal selenide via doping and interface engineering in sodium storage.

Study On Electrolyte of Low Temperature Sodium-Ion Battery

With the rapid development of electronic devices, energy storage systems with excellent performance are required. To be used in cold climates and high-altitude areas, it is required that the battery should work stably and operate safely even when the temperature drops below freezing point. Sodium-ion batteries arouse great attention, because of their high safety, good capacity in both high and low-temperature environments, along with their abundant sodium resources in the earth's crust. But for practical applications, the kinetics of sodium-ion batteries become slow when working at low temperatures. The performance deteriorates with the temperature decreases. Therefore, researchers have carried out a lot of research to overcome these problems in the low-temperature environment. For example, the energy storage performance of sodium-ion batteries can be improved by optimizing the positive and negative electrodes, separators, and electrolytes. Among them, optimizing the electrolyte is critical to improving the energy storage performance of sodium-ion batteries. Because the electrolyte is an important part, which is in contact with each part of the battery as a medium, which is mainly composed of solvents, electrolyte salts, and additives. During the charge/discharge processes of the battery, the electrolyte plays a role to act as an ionic conductor to transfer Na + between the positive and negative electrodes and link then together. Additionally, the electrolyte will also directly participate in the reaction on the electrode surface and form SEI film. Thus, it is one of the most economical and effective means to enhance the low-temperature performance by modifying the electrolyte. This paper, summarizing the reports on the electrolyte of low-temperature sodium-ion batteries at home and abroad, sorting out and analyzing the solid, liquid, and gel electrolytes, clarifies how to making the electrochemical performance of sodium-ion batteries better by optimizing electrolytes.

Unraveling the atomic-level manipulation mechanism of tin-based ternary anodes via hetero-anion engineering for stable sodium ion storage

The gradual retardation of heterogeneous interface reactions during extended cycling results in significant capacity loss, particularly in the initial few cycles. This is due to the inhomogeneous distribution and structural degradation of heterointerfaces. Currently, a range of atomic-level tuning strategies are employed to enhance the intrinsic transfer characteristics for sodium-ion batteries (SIBs). Herein, the defect-rich single-phase ternary tin sulfide selenide (SnSe1.33S0.67) anode is constructed via favorable heteroatom(S) introducing. Such a defective open structure employed as anodes for SIBs, delivers a superior rate performance of 452.3 mAh g−1 at 5.0 A g−1, and excellent cycling stability, with a capacity retention of 535.8 mAh g−1 after 500 cycles at 1.0 A g−1. The exceptional performance is attributed to the rapid diffusion of ions/electrons through lattice defects and heteroatom coexistence, as well as the high tolerance for volume changes resulting from optimized phase transition modes and enhanced structural rigidity, as demonstrated by experimental results and density functional theory (DFT) calculations. Through the heteroatoms injection strategy, this work offers deeper insights into the correlation between precise regulation of internal defects and superior storage performance in SIBs.

Flash-pyrolyzed coal char as a high-performance anode for sodium-ion batteries

This work explores a novel approach for improving the sodium-ion battery performance of coal char using flash pyrolysis and an ether-based electrolyte. Coal char is an ultra-low cost hard carbon with promising application as an anode material in sodium-ion batteries. During flash pyrolysis, char is heated at 1000 °C/s in a drop-tube furnace to create a highly-irregular structure. The larger d-spacing and smaller closed micropore diameter of flash-pyrolyzed char increases anode capacity compared to traditional slow-pyrolyzed char electrodes. The sodium-ion battery anode performance of flash-pyrolyzed char is further improved using an ether-based electrolyte in place of the traditional ester-based electrolyte. Performance improvements include greater initial Coulombic efficiency (58% in ester- vs. 64% in ether-based electrolyte) and improved specific capacity in an ether-based electrolyte. Overall, the combination of flash pyrolysis and ether-based electrolyte increases the sodium-ion battery discharge capacity of coal char by over 50%, from 72.5 mAh g−1 (slow-pyrolyzed char in ester-based electrolyte) to 109.4 mAh g−1 (flash-pyrolyzed char in ether-based electrolyte) (50 mA g−1 discharge rate). The results highlight improvements that can be realized through flash pyrolysis of coal char for battery applications and the numerous processing advantages of flash vs. slow pyrolysis.

Regulation of collagen-derived carbon material structures through in-situ precipitation templating for fast sodium storage

Limited capacity with sluggish Na+ diffusion kinetics limits the application of carbon anodes in sodium ion batteries (SIB). Herein, we present a straightforward approach for fabricating porous carbons with delicate structural regulation using collagen fibers as precursor, in-situ generated Mg(OH)2 as template. The utilization of small-sized Mg(OH)2 facilitates the formation of mesopores further to enhance the diffusion kinetics of Na⁺. The collagen fiber precursors contain abundant N and S elements, resulting in N, S co-doping. Leveraging the absorption mechanism facilitated by rapid charge transfer, the synthesized porous carbon exhibits exceptional SIB performance in ether-based electrolytes: a capacity of 459 mAh g−1 at 0.05 A g−1 and 125 mAh g−1 at 50 A g−1; a capacity of 128 mAh g−1 with an average Coulombic efficiency of ≈99 % and a decay rate of 0.0072 % per cycle after 5000 cycles at 10 A g−1. Coupled with Na3V2(PO4)3 cathode, the fabricated full cell also demonstrates a high specific capacity of 290 mAh g−1 at 0.2 A g−1 with an initial Coulombic efficiency of 75.6 %. These findings offer an effective and practical strategy for the fabrication of porous carbon materials and the advancement of SIB through the development of advanced carbon anodes.

Enhancing sodium-ion battery performance through crystalline water-assisted Zn2V2O7 anode material

To make sodium-ion batteries (SIBs) commercially viable, progress in advanced electrode materials has been witnessed to overcome unsatisfactory performance, including low charging/discharging efficiency and short lifespan. Recently, Zn2V2O7 (ZVO) has emerged as a bright anode arising from the distinctive crystal structure and electrochemical properties. Here, the novel approach is utilized to produce ZVO nanoparticles via a combination of wet chemistry and low-temperature solid-phase techniques. More explicitly, the specific discharge capacities of the ZVO-350 anode remain 141.6 mAh g−1 over 100 cycles at 50 mA g−1, demonstrating outstanding cycle stability. Significantly, in-situ X-ray diffraction (XRD) analysis is performed to reveal the operational mechanism and phase transitions of ZVO. Furthermore, the kinetic analysis of ZVO anode is unveiled through pseudo-capacitance calculation and GITT tests. Finally, variable temperature Raman spectroscopy is employed in-situ to test the changes of ZVO with increasing temperature aiming to assess the effect of cooling rate on the ZVO. This work establishes a suitable ZVO anode for SIBs and highlights the formidable energy storage potential in a competitive landscape.

Achieving high-rate capacity FeSe2@N-Doped carbon decorated with Ti3C2Tx MXenes for sodium ion batteries

Transition metal selenides have been studied as potential anodes for sodium-ion batteries (SIBs) due to their high theoretical capacity and electric conductivity. However, the serious volume expansion, particle aggregation and the dissolution of polyselenium can lead to inferior cycle performance. Herein, the ingeniously designed FeSe2 hollow spheres with the nitrogen-doped carbon shells and Ti3C2Tx MXene materials have been synthesized and exhibited the excellent rate and cycle performance for SIBs, achieving the specific capacity of 344 mAh g−1 with the charging process of ∼26.4 s at 50 A g−1 and the reversible capacity of 287 mAh g−1 after 1200 cycles. The synergy effect of nitrogen-doped carbon shells and MXene layers with the inner void can facilitate mass transport/electron transfer, alleviate the volume expansion of FeSe2, and reduce the direct contact of FeSe2 with the electrolyte, satisfying the sodium storage performance and ultrahigh stability. Moreover, the full cells assembled with pre-sodiated FeSe2@NC@MXene as anode and Na3V2(PO4)3@C as cathode deliver a reversible capacity of 466 mAh g−1 after 600 cycles at 1 A g−1, with a capacity retention rate of 90.3 %. This work may present a promising way for the high-rate capacity materials for the applications as sodium-ion battery anode.

NaSn0.02Ti1.98(PO4)3/C as a promising anode material with high performance for sodium-ion batteries

NaSn0.02Ti1.98(PO4)3/C as a promising anode material with high performance for sodium-ion batteries

Intrinsic Defect and Deformation on Local Structure Caused by Rare‐Earth Ions in the Na3V2(PO4)2F3 Cathode Material

Na3V2(PO4)2F3 has been attracting a lot of attention as a positive electrode material for sodium‐ion batteries (SIBs). The deformation of local structure caused by rare‐earth ions and intrinsic defect properties in Na3V2(PO4)2F3 as a positive electrode for SIB have been investigated with atomistic simulation based on the lattice energy minimization. A good reproduction of the Na3V2(PO4)2F3 structure is obtained. It is revealed that Na Frenkel defect, which is formed by sodium interstitial and vacancy pair, is the most favorable type of intrinsic defect. This leads to the formation of stable sodium vacancy required for the Na‐ion diffusion. The results indicate that trivalent rare‐earth dopants at the V3+ site are the most energetically favorable dopants for Na3V2(PO4)2F3, and that the incorporation at the Na and P site could be used as a strategy to increase the sodium vacancy and interstitial, respectively. The deformation in the local structure by the rare‐earth ions doping at the V site is also investigated as helpful in improving the rate performance of SIBs.

Na2.60Fe1.70(SO4)3 particles embedded in cross-linked graphene oxide networks as high-performance dual-electrode for sodium-ion batteries

Sodium iron sulfate materials have been initially applied to sodium ion batteries (SIBs) owing to their high operating voltage and stable electrochemical properties, yet poor conductivity and low theoretical capacity limit its commercial development. Herein, we first prepared Na2.60Fe1.70(SO4)3@graphene oxide (GO) composite via a facile solid-phase ball milling strategy, which are Na2.60Fe1.70(SO4)3 particles embedded in cross-linked GO networks. For the cathode of SIBs, the active particles in the material are wrapped with cross-linked GO networks that increases the electrolyte penetration and ion transport channels as well as improves electronic conductivity, resulting in a high operating voltage of 3.74 V and excellent cycle stability (retains over 70 % of capacity after 500 cycles at 8 C). Notably, the as-prepared material could exhibit a reversible capacity of 100 mAh g−1 after 100 cycles at 0.2 C as anode for SIBs. Furthermore, the material was first used to assemble symmetric sodium-ion full cell, demonstrating excellent electrochemical performance (achieving 60 mAh g−1 at 0.2 C). The Na2.60Fe1.70(SO4)3 particles wrapped with cross-linked GO networks offer a simple and effective approach to enhance the performance of SIBs, making an important contribution towards their practical industrial application.