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Due to their high specific capacity and long cycle life, bimetallic sulfides are the preferred choice of researchers as anodes in sodium-ion batteries (SIBs). However, studies indicate that this class of materials often requires expensive elements such as Co, Sb, Sn, etc., and their performance is insufficient with the use of inexpensive Fe, V alone. Therefore, there is a need to explore the relationship between metal cations and anode performance so that the requirements of cost reduction and performance enhancement can be met simultaneously. In this work, a series of partially replaced sulfides with different cation ratios have been prepared by a hydrothermal method followed by heat treatment. By partially replacing Co in NiCo sulfides, all samples show improved capacity and stability over the original NiCo sulfides. As a result, the metal elements have different oxidation states, which leads to a higher capacity through their synergistic effects on each other. Mn-NiCoS with 10% replacement showed satisfactory capacity (721.09 mAh g−1 at 300 mA g−1, 662.58 mAh g−1 after 20 cycles) and excellent cycle life (85.41% capacity retention after 1000 cycles at 2000 mA g−1). [ABSTRACT FROM AUTHOR]

Despite their variable valence and favorable sodiation/desodiation potential, vanadium sulfides (VSx) used as anode materials of sodium‐ion batteries (SIBs) have been held back by their capacity decline and low cycling capability, associated with the structure distortion volume expansion and pulverization. This study reports an accessible process to tackle these challenges via fabricating a 3D‐VSx anode for SIBs with ultrahigh‐rate and ultralong‐duration stable sodium storage. The sodiation‐driven reactivation of micro‐nano 3D‐VSx activates the reconfiguration effect, effectively maintaining structural integrity. Interestingly, the mechanical degradation of 3D‐VSx over the sodiation process can be controlled by fine‐tuning the operating voltage. The self‐reconfigured open nanostructures with large void space not only effectively withstand repetitive volume changes and mitigate the damaging mechanical stresses, but also in turn construct a self‐optimized shortened ion diffusion pathway. Moreover, the sodiation‐driven reconfiguration excites many active sites and optimizes a stable solid‐electrolyte interface, thereby delivering a reversible capacity of 961.4 mA h g−1 after 1500 cycles at a high rate of 2 A g−1. This work provides new insight into the rational design of electrodes toward long‐lived SIBs through sodiation‐driven reconfiguration. [ABSTRACT FROM AUTHOR]

Transition metal oxides have a great potential in sodium‐ion capacitors (SICs) due to their pronouncedly higher capacity and low cost. However, their poor conductivity and fragile structure hinder their development. Herein, core‐shell‐like nickel‐cobalt oxysulfide (NCOS) nanowires are synthesized and demonstrated as an advanced SICs anode. The bimetallic oxysulfide with multiple cation valence can promote the sodium ion adsorption and redox reaction, massive defects enable accommodation of the volume change in the sodiation/desodiation process, meanwhile the core‐shell‐like structure provides abundant channels for fast transfer of sodium ions, thereby synergistically making the NCOS electrode exhibit a high reversible sodium ion storage capacity (1468.5 mAh g−1 at 0.1 A g−1) and an excellent cyclability (90.5% capacity retention after 1000 cycles). The in‐situ X‐ray diffraction analysis unravels the insertion and conversion mechanism for sodium storage in NCOS, and the enhanced capability of NCOS is further verified by the kinetic analysis and theoretical calculations. Finally, SICs consisting of the NCOS anode and a boron‐nitrogen co‐doped carbon nanotubes cathode deliver an energy density of 205.7 Wh kg−1, a power density of 22.5 kW kg−1, and an outstanding cycling lifespan. These results indicate an efficient strategy in designing a high‐performance anode for sodium storage based on bimetallic dianion compounds. [ABSTRACT FROM AUTHOR]

A ceramic in polymer hybrid solid electrolyte (HSE) based on a poly vinylidene fluoride-hexafluoropropylene (PVDF-HFP) polymer comprising Na3Zr2Si2PO12 (NASICON) ceramic particles was prepared by a simple solution casting method followed by activation in a liquid electrolyte. The prepared HSE exhibits good flexibility, high ionic conductivity of 2.25 × 10−3 S cm−1 at room temperature (RT), and good interface stability. The carbon coated sodium vanadium phosphate (Na3V2(PO4)3/C) cathode was synthesized by the sol-gel method and assembled into batteries with different electrolytes. The batteries based on HSE exhibit better electrochemical performance than that of NASICON ceramic solid electrolytes, which delivers a reversible capacity of 98 mAh · g−1 at 0.2 C and exhibits good capacity retention of 85% after 175 cycles at 0.5 C. Not only does the HSE inherit great flexibility, but also exhibits good interfacial contact with electrodes. The schematic diagram of Na-ion conductivity in ceramic, polymer and HSE was illustrated to demonstrate the sodium ion transport mechanism. The HSE with high ionic conductivity and good flexibility for interfacial contact with electrodes shall provide a designing strategy for different solid-state batteries. [ABSTRACT FROM AUTHOR]

In response to the increased demands of available energy storage, sodium ion batteries (SIBs) appear as promising alternatives to widely used lithium ion batteries. However, because of large radius of Na ions, more complex requirements for the intrinsic properties raise the difficulties in finding a suitable material, in particularly for electrodes with intercalation mechanism. Concerning the principle of designing effective electrodes, the ordering of atomic arrangements should be at the heart in SIBs due to its significant influences on various electrochemical processes, such as ion absorption, ion diffusion, electron diffusion, etc. As proof-of-concept, the state-of-the art TiO2 electrodes with different orderliness of atomic arrangement are achieved through colloidal crystal template method assisted by low-temperature atomic layer deposition and post-heating treatment. The disordering at the surface is benefit for the contribution from surface processes, which is particularly significant to the electrode materials with poorer affinity of transporting ions. Meanwhile, the disordering in bulk results in better ion diffusion, but worse electron transport. Understanding this relationship between atomic orderliness and battery performance is of importance for extending the design principle to some traditional electrodes for highly effective energy storage. [ABSTRACT FROM AUTHOR]

Rechargeable ion batteries have contributed immensely to shaping the modern world and been seriously considered for the efficient storage and utilization of intermittent renewable energies. To fulfill their potential in the future market, superior battery performance of high capacity, great rate capability, and long lifespan is undoubtedly required. In the past decade, along with discovering new electrode materials, the focus has been shifting more and more toward rational electrode designs because the performance is intimately connected to the electrode architectures, particularly their designs at the nanoscale that can alleviate the reliance on the materials' intrinsic nature. The utilization of nanoarchitectured arrays in the design of electrodes has been proven to significantly improve the battery performance. A comprehensive summary of the structural features and fabrications of the nanoarchitectured array electrodes is provided, and some of the latest achievements in the area of both lithium- and sodium-ion batteries are highlighted. Finally, future challenges and opportunities that would allow further development of such advanced electrode configuration are discussed. [ABSTRACT FROM AUTHOR]

Organic sodium-ion batteries (SIBs) are one of the most promising alternatives of current commercial inorganic lithium-ion batteries (LIBs) especially in the foreseeable large-scale flexible and wearable electronics. However, only a few reports are involving organic SIBs so far. To achieve fast-charge and fast-discharge performance and the long-term cycling suitable for practical applications, is still challenging. Here, important factors for high performance SIBs especially with high capacity and long-term cyclability under fast-charge and fast-discharge process are investigated. It is found that controlling the solubility through molecular design and determination of the electrochemical window is essential to eliminate dissolution of the electrode material, resulting in improved cyclability. The results show that poly(vinylidenedifluoride) will decompose during the charge/discharge process, indicating the significance of the binder for achieving high cyclability. Beside of these, it is also shown that decent charge transport and ionic diffusion are beneficial to the fast-charge and fast-discharge batteries. For instance, the flake morphology facilitates the ionic diffusion and thereby can lead to a capacitive effect that is favorable to fast charge and fast discharge. [ABSTRACT FROM AUTHOR]

The utilization of oxygen vacancies (OVs) in sodium ion batteries (SIBs) is expected to enhance performance, but as yet it has rarely been reported. Taking the MoO3− x nanosheet anode as an example, for the first time we demonstrate the benefits of OVs on SIB performance. Moreover, the benefits at deep-discharge conditions can be further promoted by an ultrathin Al2O3 coating. A series of measurements show that the OVs increase the electric conductivity and Na-ion diffusion coefficient, and the promotion from ultrathin coating lies in the effective reduction of cycling-induced solid-electrolyte interphase. The coated nanosheets exhibited high reversible capacity and great rate capability with the capacities of 283.9 (50 mA g−1) and 179.3 mAh g−1 (1 A g−1) after 100 cycles. This work may not only arouse future attention on OVs for sodium energy storage, but also open up new possibilities for designing strategies to utilize defects in other energy storage systems. [ABSTRACT FROM AUTHOR]

Rechargeable sodium-ion batteries (SIBs) have attracted great attention for large-scale electric energy storage applications and smart grid owing to the abundance of Na resources and comparable performance with lithium-ion batteries. The use of organic electrode materials enables a sodium storage system with high energy/power density, metal-free, environmental friendliness, flexibility, lightweight, and cost-effectiveness. More importantly, the structural diversity and the ease of functionalizing organic molecules allows straightforward controllability on the redox properties and thus on the battery performances. Despite the development of organic SIBs is still in its infant state, they have drawn dramatically growing attentions and shown great promises throughout research works. In this review, we summarize the research efforts to push forward the electrochemical performance of the organic SIBs. We explore the efforts made on molecular design and electrode design, and the combination of both forms the basis to regulate the electrochemical properties. Moreover, we summarize the strategies for reducing the solubility of the organic electrode materials in light of the importance of this issue. The crucial differences between organic lithium-ion batteries and organic SIBs are presented. Finally, future challenges and opportunities of further developing organic electrode materials are discussed. [ABSTRACT FROM AUTHOR]

Abstract An original electrode, 3D TiO 2 @C core/shell nanobelt arrays with controllable carbon coating thickness, was successfully constructed in this work. The 3D TiO 2 nanobelts were directly grown on Ti foil, and then were coated with a layer of metal-organic framework (MOF). After thermal annealing, a porous carbon layer with tunable thickness was coated onto the 3D TiO 2 nanobelts through changing the MOF thickness. The as-prepared TiO 2 @C-2 h with 5-nm-thick carbon layer presented an excellent discharge capacity of 210.5 mAh g−1 after 100 cycles at a current density of 50 mA g−1, which is 38% higher than that of pure TiO 2 electrode without carbon coating. Moreover, it can maintain a reversible capacity of 141 mAh g−1 after 1000 cycles at a current density of 200 mA g−1, and a good rate performance with 33% of capacity retention when the current density increasing from 50 to 5000 mA g−1. All the results indicate that the TiO 2 @C core/shell nanobelt array is a promising anode for sodium-ion batteries. Highlights • 3D TiO 2 nanobelt arrays possess short ion transport distance. • Coating of porous carbon layer can solve low rate capability and poor stability. • Carbon coating can be tuned by MOF thickness to get optimal performance. • Ideal 3D TiO 2 @C nanobelt-SIB exhibit superior reversible capacity and rate capability. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have recently attracted intensive attentions as a potential alternative to LIBs for large-scale energy storage applications. However, one of the major challenges to the commercialization of SIBs is the limited choice of anode materials that can offer high rate capability. In this regard, we report intertwined Cu 3 V 2 O 7 (OH) 2 ·2H 2 O nanowires/carbon fibers composite, fabricated by a facile hydrothermal method, as the anode material for SIBs. It shows s a highly reversible Na-ion storage capacity of 287.4 mAh g −1 after 50 cycles at a large current density of 0.5 A g −1 , and excellent rate performance of delivering 206.5 and 127.7 mAh g −1 after 50 cycles at high current densities of 5 and 10 A g −1 , respectively. The promising performance is ascribed to both the crystal structure of Cu 3 V 2 O 7 (OH) 2 ·2H 2 O with a large interlayer spacing, and unique intertwined network morphology of CuVOH-NWs/CFs composite in which CuVOH-NWs and CFs synergistically functioned. This work will pave a way to develop more metal vanadates materials as anodes for high-performance SIBs. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) representan effective energy storagetechnology with potentially lower material costs than lithium ionbatteries. Here, we show that the electrochemical performance of SIBs,especially rate capability, is intimately connected to the electrodedesign at the nanoscale by taking anatase TiO2as an example.Highly ordered three-dimensional (3D) Ni-TiO2core–shellnanoarrays were fabricated using nanoimprited AAO templating techniqueand directly used as anode. The nanoarrays delivered a reversiblecapacity of ∼200 mAh g–1after 100 cyclesat the current density of 50 mAh g–1and were ableto retain a capacity of ∼95 mAh g–1at thecurrent density as high as 5 A g–1and fully recoverlow rate capacity. High ion accessibility, fast electron transport,and excellent electrode integrity were shown as great merits to obtainthe presented electrochemical performance. Our work demonstrates thepossibility of highly ordered 3D heterostructured nanoarrays as apromising electrode design for Na energy storage to alleviate thereliance on the materials’ intrinsic nature and provides aversatile and cost-effective technique for the fabrication of suchperfectly ordered nanostructures. [ABSTRACT FROM AUTHOR]

To address the volume expansion as well as improve the cycling stability and specific capacity of metal selenides, hollow NiCoMnSe (NCMSe) sub-microspheres are synthesised. The as-obtained NCMSe electrodes exhibit superior performance in both LIBs and SIBs and may open up a novel avenue for the rational design of anode materials for both LIBs and SIBs. • A novel trimetallic selenide hollow sphere is prepared for LIB/SIB anodes. • The material exhibits synergistic effect and multielectron redox reactions. • The material shows excellent electrochemical performance. • The ex-situ XRD and XPS provide insight into Li+/Na+ storage mechanism. Highly conductive metal selenides have drawn increasing attention in the field of energy storage. Unfortunately, their application is severely limited by the inferior capacity contribution as well as unsatisfactory cycling stability. Here, we propose a simple and practical way to prepare hollow nickel–cobalt–manganese selenides (NCMSe) submicrospheres. The NCMSe submicrospheres exhibit rich redox reactions during the reaction process into which much more alkali metal ions can be inserted, leading to high reversible capacity and their hollow structure facilitates the contact between the active material and electrolyte to accelerate the redox kinetics. Benefiting from these features, the hollow NCMSe submicrospheres show superior Li–storage capacity (1600 mAh g−1 after 1000 cycles at 2 A g−1) and Na–storage capacity (695 mAh g−1 after 200 cycles at 0.1 A g−1). This work offers a novel insight to the remarkable electrochemical performance anode materials for both lithium and sodium ion batteries. [ABSTRACT FROM AUTHOR]