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Mixed‐anion‐group Fe‐based phosphate materials, such as Na4Fe3(PO4)2P2O7, have emerged as promising cathode materials for sodium‐ion batteries (SIBs). However, the synthesis of pure‐phase material has remained a challenge, and the phase evolution during sodium (de)intercalation is debating as well. Herein, a solid‐solution strategy is proposed to partition Na4Fe3(PO4)2P2O7 into 2NaFePO4 ⋅ Na2FeP2O7 from the angle of molecular composition. Via regulating the starting ratio of NaFePO4 and Na2FeP2O7 during the synthesis process, the nonstoichiometric pure‐phase material could be successfully synthesized within a narrow NaFePO4 content between 1.6 and 1.2. Furthermore, the proposed synthesis strategy demonstrates strong applicability that helps to address the impurity issue of Na4Co3(PO4)2P2O7 and nonstoichiometric Na3.4Co2.4(PO4)1.4P2O7 are evidenced to be the pure phase. The model Na3.4Fe2.4(PO4)1.4P2O7 cathode (the content of NaFePO4 equals 1.4) demonstrates exceptional sodium storage performances, including ultrahigh rate capability under 100 C and ultralong cycle life over 14000 cycles. Furthermore, combined measurements of ex situ nuclear magnetic resonance, in situ synchrotron radiation diffraction and X‐ray absorption spectroscopy clearly reveal a two‐phase transition during Na+ extraction/insertion, which provides a new insight into the ionic storage process for such kind of mixed‐anion‐group Fe‐based phosphate materials and pave the way for the development of high‐power sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

With the rapid improvement of compact smart devices, fabricating anode materials with high volumetric capacity has gained substantial interest for future sodium‐ion batteries (SIBs) applications. Herein, a novel bimetal sulfide CuCo5S8 material is proposed with enhanced volumetric capacity due to the intrinsic metallic electronic conductivity of the material and multi‐electron transfer during electrochemical procedures. Due to the intrinsic metallic behavior, the conducting additive (CA) could be removed from the electrode fabrication without scarifying the high rate capability. The CA‐free CuCo5S8 electrode can achieve a high volumetric capacity of 1436.4 mA h cm−3 at a current density of 0.2 A g−1 and 100 % capacity retention over 2000 cycles in SIBs, outperforming most metal chalcogenides, owing to the enhanced electrode density. Reversible conversion reactions are revealed by combined measurements for sodium systems. The proposed new strategy offers a viable approach for developing innovative anode materials with high‐volumetric capacity. [ABSTRACT FROM AUTHOR]

Nano-structure designs with conductive networks have been demonstrated as an efficient strategy to boost sodium storage properties for transition metal sulfides. Herein, an exquisite nanosheets self-assembled hierarchical flower-ball-like CuFeS2 embedded into the reduced graphene oxide (RGO) nanosheet matrix (F-CuFeS2@RGO) is fabricated via a concise two-step solvothermal method. Such a well-designed architecture affords increased active reaction interfaces and enhanced mixed ionic/electronic conductivity. Meanwhile, the external RGO matrix can effectively alleviate the volume expansion and create a stable structure during long cycles. As a result, the composite material exhibits a high reversible capacity of 559 mAh·g−1 at 0.1 A·g−1, a superior rate capability of 455 mAh·g−1 at 5 A·g−1 and excellent cyclic stability with 96% capacity retention after 4800 cycles at 5 A·g−1, among the best in the state-of-the-art transition metal sulfide anodes. Especially, F-CuFeS2@RGO delivers outstanding low-temperature performances with a high capacity retention of 100% and 91% at −20 and −40 °C, respectively, over 200 cycles. The proposed hierarchical structure fabrication paves a new direction in the design of high-performance electrodes for all-temperature energy storage applications. [ABSTRACT FROM AUTHOR]

Layered vanadium‐based oxides are the promising cathode materials for aqueous zinc‐ion batteries (AZIBs). Herein, an in situ electrochemical strategy that can effectively regulate the interlayer distance of layered NH4V4O10 quantitatively is proposed and a close relationship between the optimal performances with interlayer space is revealed. Specifically, via increasing the cutoff voltage from 1.4, 1.6 to 1.8 V, the interlayer space of NH4V4O10 can be well‐controlled and enlarged to 10.21, 11.86, and 12.08 Å, respectively, much larger than the pristine one (9.5 Å). Among them, the cathode being charging to 1.6 V (NH4V4O10‐C1.6), demonstrates the best Zn2+ storage performances including high capacity of 223 mA h g−1 at 10 A g−1 and long‐term stability with capacity retention of 97.5% over 1000 cycles. Such superior performances can be attributed to a good balance among active redox sites, charge transfer kinetics, and crystal structure stability, enabled by careful control of the interlayer space. Moreover, NH4V4O10‐C1.6 delivers NH4+ storage performances whose capacity reaches 296 mA h g−1 at 0.1 A g−1 and lifespan lasts over 3000 cycles at 5 A g−1. This study provides new insights into understand the limitation of interlayer space for ion storage in aqueous media and guides exploration of high‐performance cathode materials. [ABSTRACT FROM AUTHOR]

Bimetallic transition metal chalcogenides (TMCs) materials have emerged as attractive anodes for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) because of the high intrinsic electronic conductivity, rich redox sites and unique reaction mechanism. In this work, we report the synthesis and electrochemical properties of a novel bimetallic TMCs material CuSbSe2. The as‐prepared anode delivers a high reversible capacity of 545.6 mA h g−1 for SIBs and 592.6 mA h g−1 for LIBs at a current density of 0.2 A g−1, and an excellent rate capability of 425.9 mA h g−1 at 20 A g−1 for SIBs and 226.0 mA h g−1 at 10 A g−1 for LIBs without any common‐used surface modification or carbonaceous compositing. In addition, ex situ X‐ray diffraction (XRD) and High‐resolution transmission electron microscopy (HRTEM) reveal a combined conversion‐alloying reaction mechanism of LIBs and NIBs. Our findings suggest bimetallic CuSbSe2 could be a potential anode material for both SIBs and LIBs. [ABSTRACT FROM AUTHOR]

Silicon is widely developed and deemed as a hopeful anode material for lithium‐ion batteries. However, till now there is very little literature devoted to its study for sodium‐ion batteries (SIBs). One possible reason is the preparation difficultly of carefully crafted amorphous silicon (a‐Si) structures by a facile and low‐cost method. Another reason is that a‐Si suffers from large volume expansion, slow sodium diffusion kinetics, and poor electrical conductivity. Herein, a new method called as "sodiothermic reduction" is used to prepare a‐Si hollow nanospheres at a much lower temperature. Moreover, an a‐Si‐based composite with yolk‐shell structure is designed via atomic layer deposition of alumina, in situ chemical polymerization of pyrrole, and dilute HCl etching. The obtained composite as an anode material for SIBs displays a great initial discharge capacity of 645.6 mAh g–1 at 100 mA g–1, superior long steadiness up to 5000 cycles at 800 mA g–1, and preeminent rate capability (646.4, 193.5, 138.6, 105, 77.5 mAh g–1 at 100, 400, 800, 1500, 3000 mA g–1, respectively). In situ transmission electron microscopy observation on the structure evolution and finite element analysis of the stress–strain behavior are combined to further prove the merits of the well‐designed yolk–shell structure. [ABSTRACT FROM AUTHOR]

Selenium‐based materials are considered as desirable candidates for potassium‐ion and sodium‐ion storage. Herein, an in situ fabrication method is developed to prepare an integrated cuprous selenide electrode by means of directly chemical selenization of the copper current collector with commercial selenium powder. Interestingly, only the electrolyte of 1 m potassium hexafluorophosphate dissolved in 1,2‐dimethoxyethane with higher highest occupied molecular orbital energy and lower desolvation energy facilitates the formation of polyselenide intermediates and the further selenization of the copper current collector. Benefiting from the unique thin‐film‐like nanosheet morphology and the robust structural stability of the integrated electrode, the volume change and the loss of selenide species could be effectively restrained. Therefore, high performance is achieved in both potassium‐ion batteries (462 mA h g−1 at 2 A g−1 for 300 cycles) and sodium‐ion batteries (775 mA h g−1 at 2 A g−1 for 4000 cycles). The facile fabrication strategy paves a new direction for the design and preparation of high‐performance electrodes. [ABSTRACT FROM AUTHOR]

Detrimental dendritic lithium (Li) growth, infinite volume expansion of Li deposition and inevitable excess electrolyte consumption have always impeded the successful application of Li metal anodes. Herein, a unique lithiophilic vertical cactus‐like framework (LVCF) derived from a Zn/Cu‐based coordination polymer through in situ chemical etching of Cu foam is proposed to enhance the safety and electrochemical performance of Li metal anodes. An ingenious strategy of releasing Cu ions from Cu foam in the presence of organic ligands is implemented successfully to achieve the coordination polymer precursor, resulting in the coexistence of massive lithiophilic nitrogen‐containing functional groups, ZnO quantum dots and in situ grown carbon nanotubes (CNTs) in the LVCF, which is beneficial to avoiding the generation of harmful Li dendrites. Benefiting from the positive effects of the improved lithiophilicity, decreased local current density and relieved volume expansion, LVCF delivers an ultrastable Coulombic efficiency of 98.6% for 600 cycles at 1 mA cm–2 and an improved cycling lifespan of 1800 h for symmetric cells. Full cells comprising LVCF@Li anodes and LiFePO4 cathodes can deliver an ultrahigh capacity of 101.8 mAh g–1 (capacity retention ratio: 77.9%) after 900 cycles at 1 C and excellent rate performance. [ABSTRACT FROM AUTHOR]

Sodium‐ and potassium‐ion batteries have attracted intensive attention recently as low‐cost alternatives to lithium‐ion batteries with naturally abundant resources. However, the large ionic radii of Na+ and K+ render their slow mobility, leading to sluggish diffusion in host materials. Herein, hierarchical FeSe2 microspheres assembled by closely packed nano/microrods are rationally designed and synthesized through a facile solvothermal method. Without carbonaceous material incorporation, the electrode delivers a reversible Na+ storage capacity of 559 mA h g−1 at a current rate of 0.1 A g−1 and a remarkable rate performance with a capacity of 525 mA h g−1 at 20 A g−1. As for K+ storage, the FeSe2 anode delivers a high reversible capacity of 393 mA h g−1 at 0.4 A g−1. Even at a high current rate of 5 A g−1, a discharge capacity of 322 mA h g−1 can be achieved, which is among the best high‐rate anodes for K+ storage. The excellent electrochemical performance can be attributed to the favorable morphological structure and the use of an ether‐based electrolyte during cycling. Moreover, quantitative study suggests a strong pseudocapacitive contribution, which boosts fast kinetics and interfacial storage. [ABSTRACT FROM AUTHOR]

Abstract: Identifying suitable electrode materials for sodium‐ion and potassium‐ion storage holds the key to the development of earth‐abundant energy‐storage technologies. This study reports an anode material based on self‐assembled hierarchical spheroid‐like KTi2(PO4)3@C nanocomposites synthesized via an electrospray method. Such an architecture synergistically combines the advantages of the conductive carbon network and allows sufficient space for the infiltration of the electrolyte from the porous structure, leading to an impressive electrochemical performance, as reflected by the high reversible capacity (283.7 mA h g−1 for Na‐ion batteries; 292.7 mA h g−1 for K‐ion batteries) and superior rate capability (136.1 mA h g−1 at 10 A g−1 for Na‐ion batteries; 133.1 mA h g−1 at 1 A g−1 for K‐ion batteries) of the resulting material. Moreover, the different ion diffusion behaviors in the two systems are revealed to account for the difference in rate performance. These findings suggest that KTi2(PO4)3@C is a promising candidate as an anode material for sodium‐ion and potassium‐ion batteries. In particular, the present synthetic approach could be extended to other functional electrode materials for energy‐storage materials. [ABSTRACT FROM AUTHOR]

Abstract: Energy‐storage technology is moving beyond lithium batteries to sodium as a result of its high abundance and low cost. However, this sensible transition requires the discovery of high‐rate and long‐lifespan anode materials, which remains a significant challenge. Here, the facile synthesis of an amorphous Sn2P2O7/reduced graphene oxide nanocomposite and its sodium storage performance between 0.01 and 3.0 V are reported for the first time. This hybrid electrode delivers a high specific capacity of 480 mA h g−1 at a current density of 50 mA g−1 and superior rate performance of 250 and 165 mA h g−1 at 2 and 10 A g−1, respectively. Strikingly, this anode can sustain 15 000 cycles while retaining over 70% of the initial capacity. Quantitative kinetic analysis reveals that the sodium storage is governed by pseudocapacitance, particularly at high current rates. A full cell with sodium super ionic conductor (NASICON)‐structured Na3V2(PO4)2F3 and Na3V2(PO4)3 as cathodes exhibits a high energy density of over 140 W h kg−1 and a power density of nearly 9000 W kg−1 as well as stability over 1000 cycles. This exceptional performance suggests that the present system is a promising power source for promoting the substantial use of low‐cost energy storage systems. [ABSTRACT FROM AUTHOR]

Abstract: A facile chemical vapor deposition method is developed for the preparation of carbon nanofiber (CNF) composite Na3V2(PO4)2F3@C as cathodes for sodium‐ion batteries. In all materials under investigation, the optimized composite content, denoted as NVPF@C@CNF‐5, shows excellent sodium storage performance (86.3 % capacity retention over 5000 cycles at 20 C rate) and high rate capability (84.3 mA h g−1 at 50 C). The superior sodium storage performance benefits from the enhanced electrical conductivity of the working electrode after formation of a composite with CNF. Furthermore, the full cell using NVPF@C@CNF‐5 and hard carbon as the cathode and anode, respectively, demonstrates an impressive electrochemical performance, realizing an ultrahigh rate charge/discharge at a current rate of 30 C and long‐term stability over 1000 cycles. This approach is facile and effective, and could be extended to other materials for energy‐storage applications. [ABSTRACT FROM AUTHOR]

It remains a big challenge to identify high-performance anode materials to promote practical applications of sodium-ion batteries. Herein, the facile synthesis of CoS nanoflowers wrapped in reduced graphene oxides (RGO) is reported, and their sodium storage properties are systematically studied in comparison with bare CoS. The CoS@RGO nanoflowers deliver a high reversible capacity of 620 mAh g−1 at a current density of 100 mA g−1 and superior rate capability with discharge capacity of 329 mAh g−1 at 4 A g−1, much higher than those of the bare CoS. Evidenced by electrochemical impedance spectra and ex-situ SEM images, the improvement in the sodium storage performance is found to be due to the introduction of RGO which serves as a conducting matrix, to not only increase the kinetic properties of CoS, but also buffer the volume change and maintain the integrity of working electrodes during (de)sodiation processes. More importantly, the pseudocapacitive contribution of more than 89 % is only observed in the CoS@RGO nanocomposites, owing to the enhanced specific area and surface redox behavior. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide Li1.18Ni0.15Co0.15Mn0.52O2 (LNCM) is, for the first time, examined as the positive electrode for hybrid sodium-ion battery and its Na+ storage properties are comprehensively studied in terms of galvanostatic charge-discharge curves, cyclic voltammetry and rate capability. LNCM in the proposed sodium-ion battery demonstrates good rate capability whose discharge capacity reaches about 90 mA h g−1 at 10 C rate and excellent cycle stability with specific capacity of about 105 mA h g−1 for 200 cycles at 5 C rate. Moreover, ex situ ICP-OES suggests interesting mixed-ions migration processes: In the initial two cycles, only Li+ can intercalate into the LNCM cathode, whereas both Li+ and Na+ work together as the electrochemical cycles increase. Also the structural evolution of LNCM is examined in terms of ex situ XRD pattern at the end of various charge-discharge scans. The strong insight obtained from this study could be beneficial to the design of new layered cathode materials for future rechargeable sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Silver molybdate, Ag2Mo2O7, has been prepared by a conventional solid-state reaction. Its electrochemical properties as an anode material for sodium-ion batteries (SIBs) have been comprehensively examined by means of galvanostatic charge-discharge cycling, cyclic voltammetry, and rate performance measurements. At operating voltages between 3.0 and 0.01 V, the electrode delivered a reversible capacity of nearly 190 mA h g−1 at a current density of 20 mA g−1 after 70 cycles. Ag2Mo2O7 also demonstrated a good rate capability and long-term cycle stability, the capacity reaching almost 100 mA h g−1 at a current density of 500 mA g−1, with a capacity retention of 55 % over 1000 cycles. Moreover, the sodium storage process of Ag2Mo2O7 has been investigated by means of ex situ XRD, Raman spectroscopy, and HRTEM. Interestingly, the anode decomposes into Ag metal and Na2MoO4 during the initial discharge process, and then Na+ ions are considered to be inserted into/extracted from the Na2MoO4 lattice in the subsequent cycles governed by an intercalation/deintercalation mechanism. Ex situ HRTEM images revealed that Ag metal not only remains unchanged during the sodiation/desodiation processes, but is well dispersed throughout the amorphous matrix, thereby greatly improving the electronic conductivity of the working electrode. The 'in situ' decomposition behavior of Ag2Mo2O7 is distinct from that of chemically synthesized, metal-nanoparticle-coated electrode materials, and provides strong supplementary insight into the mechanism of such new anode materials for SIBs and may set a precedent for the design of further materials. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have attracted much interest as a low-cost and environmentally benign energy storage system, but more attention is justifiably required to address the major technical issues relating to the anode materials to deliver high reversible capacity, superior rate capability, and stable cyclability. A SnSe/reduced graphene oxide (RGO) nanocomposite has been prepared by a facile ball-milling method, and its structural, morphological, and electrochemical properties have been characterized and compared with those of the bare SnSe material. Although the redox behavior of SnSe remains nearly unchanged upon the incorporation of RGO, its electrochemical performance is significantly enhanced, as reflected by a high specific capacity of 590 mA h g−1 at 0.050 A g−1, a rate capability of 260 mA h g−1 at 10 A g−1, and long-term stability over 120 cycles. This improvement may be attributed to the high electronic conductivity of RGO, which also serves as a matrix to buffer changes in volume and maintain the mechanical integrity of the electrode during (de)sodiation processes. In view of its excellent Na+ storage performance, this SnSe/RGO nanocomposite has potential as an anode material for SIBs. [ABSTRACT FROM AUTHOR]

Highlights: A freestanding MXene-derived defect-rich TiO2@reduced graphene oxides (M-TiO2@rGO) foam electrode was fabricated. M-TiO2@rGO presents fast Na+ storage kinetics due to capacitive contribution. M-TiO2@rGO foam electrode displays a capacity retention of 90.7% after 5000 cycles. Sodium ion batteries and capacitors have demonstrated their potential applications for next-generation low-cost energy storage devices. These devices's rate ability is determined by the fast sodium ion storage behavior in electrode materials. Herein, a defective TiO2@reduced graphene oxide (M-TiO2@rGO) self-supporting foam electrode is constructed via a facile MXene decomposition and graphene oxide self-assembling process. The employment of the MXene parent phase exhibits distinctive advantages, enabling defect engineering, nanoengineering, and fluorine-doped metal oxides. As a result, the M-TiO2@rGO electrode shows a pseudocapacitance-dominated hybrid sodium storage mechanism. The pseudocapacitance-dominated process leads to high capacity, remarkable rate ability, and superior cycling performance. Significantly, an M-TiO2@rGO//Na3V2(PO4)3 sodium full cell and an M-TiO2@rGO//HPAC sodium ion capacitor are fabricated to demonstrate the promising application of M-TiO2@rGO. The sodium ion battery presents a capacity of 177.1 mAh g−1 at 500 mA g−1 and capacity retention of 74% after 200 cycles. The sodium ion capacitor delivers a maximum energy density of 101.2 Wh kg−1 and a maximum power density of 10,103.7 W kg−1. At 1.0 A g−1, it displays an energy retention of 84.7% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Due to the high discharge voltage and a favorable theoretical capacity, Na 2 FePO 4 F have been attracted much attention as the viable cathode materials for sodium-ion storage. However, the low intrinsic electronic conductivity of Na 2 FePO 4 F suppresses its practical applications. Herein, ion doping strategy is employed to improve the electrochemical performance of Na 2 FePO 4 F as the cathode of sodium ion batteries. We first used density functional theory (DFT) calculation to screen the optimum dopants by evaluating the structural, electronic and electrochemical properties of metal-doped Na 2 FePO 4 F. Our calculation results indicate that the Co-doped Na 2 FePO 4 F is the most promising candidate for practical applications. To further prove the validity of metal doping, Na 2 Fe 0.94 Co 0.06 PO 4 F/C was synthesized by sol-gel method and showed superior electrochemical performance compared with the pristine material. The specific capacity of the Na 2 Fe 0.94 Co 0.06 PO 4 F/C is 99.93 mAh g−1 at 0.2 C and the discharge capacity retention is 62.1% after 400 cycles at 1 C. Image 1 • DFT and experiment are performed to reveal the metal-doping effects on Na 2 FePO 4 F. • Co-doping enhances electronic conductivity, voltage and Na ion diffusivity. • Na 2 Fe 0.94 Co 0.06 PO 4 F/C showed better electrochemical performance than Na 2 FePO 4 F/C. [ABSTRACT FROM AUTHOR]

An innovative semiconductor-to-metal transition is proposed to effectively improve the volumetric capacity and rate capability of iron chalcogenides FeS 1-x Se x , simultaneously. A rare intrinsic Na+ intercalation pseudocapacitive charge storage is observed in the high-Se doped materials. [Display omitted] • Metallic FeS 1-x Se x was found as the first intrinsic pseudocapacitive chalcogenide. • It shows high rate capability on a micrometer scale without conducting additives. • True metallic behavior triggers the rare intrinsic intercalation pseudocapacitance. There is a burgeoning need for high-power-density sodium-ion batteries (SIBs) with compressed size, whereas it is very challenging to integrate fast kinetics and high volumetric capacity into one material. Herein, we demonstrate an effective strategy to jointly promote the power and volumetric energy densities from the perspective of materials' electronic conductivity. Via semiconductor-to-metal transition, we successfully develop the first intrinsic pseudocapacitive chalcogenide material, metallic FeS 1-x Se x (x ≥ 0.5), which shows inherent capacitor-like faradic charge storage, even when crystallizes in micrometer bulk material and operates in the absence of conducting additives. Therefore, it enables conducting-additive-free (CA-free) electrodes with high volumetric capacities of 965 mA h cm−3, which also delivers exceptional rate capability with a capacity above 392 mA h cm−3 at 50C-rate, among the best state-of-the-art SIB anodes. These superior performances can be attributed to a rare intrinsic intercalation pseudocapacitive mechanism, which is related to the nature of metallic behavior and unique layered structure. This discovery not only provides a valuable complement to our understanding of pseudocapacitive processes, but also facilitates the design of high-rate electrode materials with compressed sizes in the future. [ABSTRACT FROM AUTHOR]

Flexible FeVO 4 /Ti 3 C 2 T x film had been constructed via simple vacuum assist filtration with a unique structure. Through the synergistic action of FeVO 4 and Ti 3 C 2 T x , excellent electrochemical performance is shown in lithium ion and sodium ion batteries. [Display omitted] • 3D sandwiched structure of FeVO 4 /Ti 3 C 2 T x film improves access to active sites and facilitates the Li+/Na+ insertion/extraction. • The synergistic effect of FeVO 4 and Ti 3 C 2 T x leads to superior electrochemical performance in both Li and Na ions batteries. • The reaction mechanism of lithium ion in FeVO 4 was simply verified by in-situ XRD. Ferric vanadate (FeVO 4) is a desirable anode candidate for lithium-ion battery (LIB) and sodium-ion battery (SIB) because of its high theoretical capacity, low cost and ease of synthesis. However, its practical application is hindered by its volume expansion during the Li+/Na+ insertion/extraction and low electronic conductivity. Herein, flexible and free-standing FeVO 4 /Ti 3 C 2 T x (FVO/MX) films have been made via combining FeVO 4 nanorods and Ti 3 C 2 T x MXene sheets via a simple method of vacuum assisted filtration. In the composite films, Ti 3 C 2 T x sheets act as host and FeVO 4 nanorods are uniformly deposited onto the layers. FeVO 4 nanorods are encapsulated by Ti 3 C 2 T x sheets, forming a three-dimensional network sandwich structure. The binder-free FVO/MX films exhibited superior electrochemical performance due to the synergyy between FeVO 4 and Ti 3 C 2 T x. Specifically, when FVO/MX electrode was used in a lithium-ion battery, it delivered reversible capacity of 1179 mAh g−1 and 1125 mAh g−1 after 250 cycles at a current density of 0.1 A g−1. Besides, the FVO/MX = 2:1 anode delivered a reversible capacity of 428 mAh g−1 at 5 A g−1 and 69.5% capacity was retained after 2500 cycles. Moreover, the Na-ion storage capacity reaches 129 mAh g−1 at a high current density of 5 A g−1, showing capacity retention of 81.1% after 5000 cycles. The charging and discharging mechanism of the FVO/MX based lithiumion battery was studied by in-situ XRD technique. Owing to high metallic conductivity and 2D morphology of Ti 3 C 2 T x MXene, 3D networks can be constructed by combining other active agents, suggesting that MXene is a promising host material for the next-generation flexible energy storage devices. [ABSTRACT FROM AUTHOR]

An aqueous robust network binder is designed by ionic cross-linking reaction to coat Se cathode for the first time, achieving admirable stability of the electrode, thus ultra-high Se loading and areal capacities for Li-Se and Na-Se batteries. [Display omitted] • An aqueous robust network binder (Fe@SA) is designed by ionic cross-linking reaction to coat Se cathode for the first time. • Enhanced electrode stability by Fe@SA binder brings excellent electrochemical performance for Se cathode batteries. • An ultra-high Se loading cathode is obtained by Fe@SA binder with traditional blade coating technology. • Fe@SA binder can achieve an ultra-high reversible areal capacity of 4.9 mAh cm−2 for Li-Se battery. • The highest reversible areal capacity of 5.6 mAh cm−2 for Na-Se battery can be obtained with Fe@SA binder. Selenium is a considerable energy storage material, with presenting a one-step electrochemical reaction in a cheap carbonate-based electrolyte and providing a considerable capacity as a cathode. However, capacity loss and safety issues caused by volume changes during charge and discharge processes, as well as low mass loading, still hinder the practical development of selenium cathodes. Binder is one of the indispensable constitutions of the electrode and crucial for improving the electrochemical performance of the battery. Herein, we design an aqueous robust network binder by doping a trace amount of Fe3+ ions into sodium alginate for durable lithium/sodium-selenium batteries for the first time. With the modified binder, the capacity of the battery is increased by more than 17% at a current of 0.2C. Furthermore, it can achieve the highest Se loading made by blade coating of up to 12 mg cm−2, which brings ultra-high reversible areal capacity of 4.9 mAh cm−2 for lithium-selenium battery, and currently the highest reported reversible areal capacity currently of up to 5.6 mAh cm−2 for sodium-selenium battery. Such a well-designed binder can improve the electrochemical performance and areal capacity of selenium cathodes, thereby boosting the practical application of selenium cathodes for energy storage. [ABSTRACT FROM AUTHOR]

• For the first time, we report TiS 3 as an anode material for SIBs. • The amorphization process during the first sodiation boosts sodium storage behavior. • The sodium-ion batteries with TiS 3 anode exhibit low charge transfer resistance. Owing to the natural abundance of sodium and the low cost of sodium resources, room temperature sodium-ion batteries are considered as attractive candidates for the next generation rechargeable batteries. To explore excellent anode materials for sodium-ion batteries, here we report TiS 3 with quasi-1D structure as a potential electrode material. TiS 3 micro-belts are successfully prepared via a facile solid-state reaction and demonstrated to be a desirable anode material. When applied in sodium-ion batteries, the TiS 3 delivers a high reversible capacity of 346.3 mAh g−1 at 2 A g−1 after 500 cycles and excellent rate capability of 192.5 mAh g−1 at 10 A g−1. The impressive sodium storage behavior can be attributed to the amorphization process during sodiation, the surface-controlled pseudocapacitive behavior as well as the low charge transfer resistance. The unique behavior of TiS 3 could provide new insights on the design of transition metal trichalcogenides as promising anode materials for sodium storage. [ABSTRACT FROM AUTHOR]