Na-ion Storage Performance Research Articles

MAX-phase Derived Tin Diselenide for 2D/2D Heterostructures with Ultralow Surface/Interface Transport Barriers toward Li-/Na-ions Storage.

2D tin diselenide and its derived 2D heterostructures have delivered promising potentials in various applications ranging from electronics to energy storage devices. The major challenges associated with large-scale fabrication of SnSe2 crystals, however, have hindered its engineering applications. Herein, a tin-extraction synthetic method is proposed for producing large-size SnSe2 bulk crystals. In a typical synthesis, a Sn-containing MAX phase (V2 SnC) and a Se source are heat-treated under a reducing atmosphere, by which Sn is extracted from the V2 SnC phase as a rectified Sn source to form SnSe2 crystals in the cold zone. After the following liquid exfoliation, the obtained 2D SnSe2 nanosheets have a lateral size of a few centimeters and an atomic thickness. Furthermore, by coupling with 2D graphene to form 2D/2D SnSe2 /graphene heterostructured electrodes, as validated by theoretical calculation and experimental studies, the superior Li-/Na-ion storage performance with ultralow surface/interface ion transport barriers are achieved for rechargeable Li-/Na-ion batteries. This innovative synthetic strategy opens a new avenue for the large-scale synthesis of selenides and offers more options into the practical application of emerging 2D/2D heterostructure for electrochemical energy storage.

Mn3O4 nanoparticles in situ embedded in TiO2 for High-Performance Na-ion capacitor: Balance between 3D ordered hierarchically porous structure and heterostructured interfaces

Sodium-ion hybrid capacitors (SICs) are recognized as a promising new energy storage devices. The design of anodes with high rates to balance the fast desorption/adsorption process in cathode is a key way to construct desirable SICs. Herein, Mn3O4 nanoparticles are in situ embedded in TiO2 to form Mn3O4@TiO2 nanocomposite as anode for SICs. The prepared Mn3O4@TiO2 nanocomposite shows hierarchically porous structure with macropores and mesopores. The Mn3O4 content in the composites can be adjusted to achieve the balance between the hierarchically porous structure and heterostructured Mn3O4/TiO2 interfaces. The optimized Mn3O4@TiO2 with ∼30 wt% Mn3O4 achieves this balance, delivering a large discharge capacity of 247.8 mAh g−1 at 1 A g−1 after 1000 cycles in SIBs. The assembled SICs by using Mn3O4@TiO2-2 as anode and commercial activated carbon as cathode can achieve a high energy and power densities of 106.5 Wh kg−1 and 10140.5 W kg−1, respectively, and an extended cycle life of 92.8 % retention after 5000 cycles. The good Na-ion storage performance mainly arises from the macropores that can provide rapid mass transfer channels, the mesopores that can offer high specific surface areas and highly dispersed Mn3O4 nanoparticles and abundant Mn3O4/TiO2 interfaces that can afford a lot of active sites.

Electrolytic Conversion of Natural Graphite into Carbon Nanostructures with Enhanced Electrical Conductivity and Na-ion Storage Performance

This article reports on the electrochemical exfoliation of natural graphite into electrolytic carbon nanostructure (ECN) containing three dimensional clusters of onion-like carbon nanoparticles and carbon nanotubes. The exfoliation process is conducted in molten LiCl-NaCl at 740 °C. The morphological and structural characteristics of ECN are correlated to its electrical and electrochemical performances. Due to the presence of highly graphitized nanotubes, the bulk electrical conductivity of ECN is found to be remarkable at 9.7 S cm−1. Also, an enlarged d002 interlayer spacing is recorded on onion-like carbon nanoparticles present in ECN, enhancing the Na-ion storage performance of the material, with the reversible capacity of 175 mAh g−1 recorded after 385 Na-ion insertion and extraction cycles at the current density of 200 mA g−1. This article discusses the molten salt conversion of natural graphite minerals into nanostructured carbon with enhanced electrical conductivity and Na-ion storage performance.

Low-temperature solid-state synthesis of interlayer engineered VS4 for high-capacity and ultrafast sodium-ion storage

The quasi-layered VS4 is the stacked linear chain structure in which parallel chains are bonded by Van der Waals forces. Considering its wide interlayer and high sulfur content, VS4 is supposed to be a potential high-performance anode material for Na-ion storage. Herein, a novel and efficient low-temperature solid-state method is developed to synthesize interlayer engineered VS4 (IE-VS4). The intercalation of [NCN]2- anion expands the interlayer of VS4 to accelerate the Na-ion diffusion. Furthermore, The intercalated anion also reduces the band gap of VS4 and enhances the electronic conductivity. Thanks to these merits, the IE-VS4 enables standout Na-ion storage performance in terms of ultrafast rate capability (500 mAh g−1 at 20 A g−1), high capacity and superior cycle stability (550 mAh g−1 at 5 A g−1 after 2500 cycles). The developed large-scale synthesis method and the interlayer engineering strategy can synergistically promote the practical application of VS4 in electrochemical energy storage.

Enhanced Structural Stability and Volumetric Capacity of a 3D Pyknotic Graphene Conductive Network via a Pillar Effect of Sn Nanoparticles for Sodium-Ion Batteries

High volumetric capacity and durability anode materials for sodium ion batteries have been urgently required for practical applications. Herein, we reported a Sn-pillared pyknotic graphene conductive network with high-level N-doping. This densely stacked block offers high volumetric Na-ion storage capacity, rapid electrochemical reaction kinetics, and robust structural stability during cycling owing to the high capacity component (metallic Sn ≈847 mAh g-1), high tap density (≈2.63 g cm-3), high conductivity (N doping ≈5 at. %), and strong spatially confined and pillared structure. Moreover, theoretical simulations have indicated that the charge accumulation around the N-doped region is more pronounced compared to the pristine one, and electrons accumulate around the N atom while loss occurs at the Na atom. These studies also suggest that it might possibly contribute to higher conductivity and stronger electrophilic reactivity, thereby resulting in enhanced Na-ion storage performance. As a result, the as-obtained electrode material exhibits competitive volumetric capacity (1462 mAh cm-3 at 0.1 A g-1), cycling performance (1207 mAh cm-3 after 100 cycles), and promising rate behavior simultaneously.

Ultrafast and ultrastable Na-ion storage in zero-strain sodium perylenetetracarboxylate anode enabled by ether electrolyte

For sodium-ion batteries (SIBs), organic anode materials, especially sodium carboxylates, received increasing attentions due to their performance potential and resource sustainability. Unfortunately, previous studies have exhibited inferior electrochemical performance, for which we speculate the use of conventional but improper ester electrolytes is responsible to a large extent. To prove it, we have systematically investigated the electrochemical performance and behaviors of two typical carboxylates, namely tetrasodium 1,4,5,8-naphthalenetetracarboxylate (Na4NTC) and tetrasodium 3,4,9,10-perylenetetracarboxylate (Na4PTC), in the typical ester and ether electrolytes. To our surprise, in the ether electrolyte, Na4PTC shows exceptional ultrafast and ultrastable Na-ion storage performance (the capacity retention is 77% at 5000 mA g–1, or 95% after 20,000 cycles), both of which set new records for organic anode materials. In-depth mechanism analysis reveals that the scarce zero-strain character of Na4PTC leading to high crystalline structure stability and high Na ion diffusion coefficient (5 × 10–10 cm2 s–1), as well as the thin and robust SEI derived from the ether electrolyte, are the internal and external factors of the excellent performance, respectively. Finally, a demonstration of Na4PTC–Na3V2(PO4)3 full-cell shows the huge potential of Na4PTC anode in practical applications, especially those emphasizing high power and long life.

Cubic Spinel XIn2S4 (X = Fe, Co, Mn): A New Type of Anode Material for Superfast and Ultrastable Na‐Ion Storage (Adv. Energy Mater. 44/2021)

Na-Ion Batteries In article number 2102137, Hui Ying Yang and co-workers develop an isomorphous series of cubic spinel XIn2S4 (X = Fe, Co, Mn) as a new type of Na-ion battery anode, displaying superfast and ultrastable Na-ion storage performance. The amazing results are due to the synergies between X substitution at the spinel's tetrahedral site and the inherent In skeleton at the octahedral sites.

Ultrafast synthesis of hard carbon anodes for sodium-ion batteries.

Hard carbons (HCs) are a significantly promising anode material for alkali metal-ion batteries. However, long calcination time and much energy consumption are required for the traditional fabrication way, resulting in an obstacle for high-throughput synthesis and structure regulation of HCs. Herein, we report an emerging sintering method to rapidly fabricate HCs from different carbon precursors at an ultrafast heating rate (300 to 500 °C min-1) under one minute by a multifield-regulated spark plasma sintering (SPS) technology. HCs prepared via the SPS possess significantly fewer defects, lower porosity, and less oxygen content than those pyrolyzed in traditional sintering ways. The molecular dynamics simulations are employed to elucidate the mechanism of the remarkably accelerated pyrolysis from the quickly increased carbon sp2 content under the multifield effect. As a proof of concept, the SPS-derived HC exhibits an improved initial Coulombic efficiency (88.9%), a larger reversible capacity (299.4 mAh⋅g-1), and remarkably enhanced rate capacities (136.6 mAh⋅g-1 at 5 A⋅g-1) than anode materials derived from a traditional route for Na-ion batteries.

Realizing Improved Sodium-Ion Storage by Introducing Carbonyl Groups and Closed Micropores into a Biomass-Derived Hard Carbon Anode.

Micropores and defects, like oxygen-containing groups, as active sites for sodium-ion storage in hard carbon have attracted considerable attention; nevertheless, most oxygen doping or oxidizing processes inevitably introduce undesired oxygen groups into a carbon framework, leading to deteriorated initial Coulombic efficiency (ICE). Here, precise carbonyl groups and closed micropores are together introduced into biomass-derived hard carbon to enhance the Na-ion storage performance. The hard carbon delivers a large reversible capacity of 354.6 mA h g-1 at 30 mA g-1, a high ICE (88.7%), as well as ultra-long cycling stability (277 mA h g-1 at 0.3 A g-1 over 1000 cycles; 243 mA h g-1 at 1 A g-1 over 5000 cycles). The rate capability and cycling stability of hard carbon in carbonate- and diglyme-based electrolytes are contrasted to demonstrate the superiority of diglyme. Cyclic voltammetry at varied scans and galvanostatic intermittent titration techniques are carried out to clarify the disparity between the two different electrolyte systems. Furthermore, the as-prepared hard carbon is utilized as the anode for sodium-ion full cells exhibiting an energy density of 166.2 W h kg-1 at 0.2 C and a long-cycle life (47.9% retention over 200 cycles at 1 C).

Constructing Bi2Se3/Bi2O3 heterostructure as promising anode for efficient sodium-ion storage

Sodium-ion batteries (SIBs) have been a promising potential alternative for sustainable electrochemical energy-storage devices. Bismuth-based materials can reserve substantial Na ions through alloying reaction and conversion reaction, leading to superior theoretical capacity. However, the alloying reaction is always accompanied by huge volume change during sodiation/desodiation processes. Herein, a flower-like Bi2Se3/Bi2O3 heterostructure is designed to address the structural degeneration problem of Bi-based materials. Diverse Bi2Se3/Bi2O3 heterostructures are produced via a facile hydrothermal reaction and subsequent annealing process, presenting apparently improved rate capability and cycling stability. Such excellent Na ion storage performance attributes to the charge redistribution around heterointerfaces caused by the unmatched band structure of two building blocks. The redistributed charges induce a dissimilar charged space nearby the phase boundaries, which not only enhance the structural integrity via coulombian force but also accelerate the diffusion of Na ions traversing heterointerfaces through electric field force. Meanwhile, the unique surface conducting states of Bi2Se3 can facilitate charge transport effectively. The initial discharge capacity of electrode reached 571 mAh/g at the current density of 0.1 A/g and maintained 310 mAh/g after 100 cycles. This work may provide a new route to enhance the structural stability of the serious volume expansion electrode materials.

Rational Design of Yolk-Shell ZnCoSe@N-Doped Dual Carbon Architectures as Long-Life and High-Rate Anodes for Half/Full Na-Ion Batteries.

Transition-metal selenides (TMSs) have emerged as prospective anode materials for sodium ion batteries (SIBs), owing to their considerable theoretical capacity and intrinsic high electronic conductivity. Whereas, TMSs still suffer from poor rate capability and inferior cycling stability induced by sluggish kinetics and severe volume changes during de/sodiation processes. Herein, a hierarchical composite consisting of a zinc-cobalt bimetallic selenide yolk and nitrogen-doped double carbon shell (denoted as ZnCoSe@NDC) is engineered and fabricated successfully. The architecture of the as-fabricated material improves the Na-ion storage performance via increasing the electron transfer kinetics, accommodating volume expansion, and mitigating the generation of by-products. As expected, the ZnCoSe@NDC electrode delivers superior sodium storage performance with long cycling stability (344.5 mAh g-1 at 5.0 A g-1 over 2000 long-term cycles) and high-rate performance (319.2 mAh g-1 at 10.0 A g-1 ). Meanwhile, the NVP@C//ZnCoSe@NDC full SIB cells are constructed successfully, retaining 96.3% of its initial capacity at 0.5A g-1 after 200 loops. The outstanding electrochemical performance and the construction of hybrid SIBs will have far-reaching influences on the development of the various rechargeable batteries.

Ni-doping induced structure distortion of MnO2 for highly efficient Na+ storage

Manganese dioxide is a typical electrode material for supercapacitor due to its high theoretical capacitance and good environmental compatibility. However, the development of MnO2 as electrode is limited by inferior conductivity, sluggish ionic transfer kinetics and poor cycling stability. Herein, we present a structure distortion strategy via Ni doping in MnO2 to boost its Na+ storage performance. The as-obtained Ni-MnO2 can deliver a high specific capacity of 379F g−1 at 1 A g−1, excellent rate performance of 281F g−1 at 20 A g−1, and a significantly enhanced cycling stability. In situ Raman results verify that Ni-MnO2 with structure distortion can achieve a promising cycling life. Density functional theory results suggest that the structure distortion can efficiently modulate electron configuration by delocalizing electron. Furthermore, the Na+ diffusion energy barrier is remarkedly decreased in Ni-MnO2, thus accelerating ionic transport kinetics. An asymmetric supercapacitor based on Ni-MnO2 cathode exhibits a high energy density of 114.6 Wh kg−1 at a power density of 3600 W kg−1. This work verifies the efficiency of structure distortion strategy on the improvement of Na ion storage performance in MnO2, which can be extended for the optimization of other electrode materials for energy storage.

Flexible Carbon Nanofibrous Membranes with Adjustable Hierarchical Porous Structure as High‐Capacity Anodes for Sodium‐Ion Batteries

Preparation of porous carbon nanofibrous membranes with excellent flexibilities and high Na ion storage capabilities to satisfy the demand of wearable energy storage devices remains challenging. Herein, a continuous and flexible porous carbon nanofibrous membrane is developed as anode material for sodium‐ion batteries by electrospinning a mixture of polyacrylonitrile (PAN) and ultrafine zeolitic imidazolate framework (ZIF‐8) nanoparticles, followed by carbonization at 1200 °C. The intrinsic porous crystal structure of ZIF‐8 and their decomposition/volatilization at high temperature assist the generation of hierarchical micro‐meso pores that are homogeneously dispersed along the nanofibers, resulting in the good flexibility and excellent Na ion storage performance. Through controlling the ZIF‐8 content at 45%, the flexible anode enables a superior Na storage capacity of 418 mA h g−1 at 0.1 A g−1 with a remarkable plateau capacity of 278 mA h g−1. The superhigh plateau capacity could be credited to the large amounts of isolated closed micro‐meso pores, implying an adsorption‐filling sodium‐ion storage mechanism. These findings provide some inspiration for the design and construction of advanced porous carbon anode materials for flexible sodium‐ion batteries.

On the Reactive Molten Salt Synthesis, Solubility and Na-Ion Storage Performance of Na2Mo2O7

A systematic investigation is conducted to evaluate the effect of temperature on the structural and morphological characteristics of Na2Mo2O7 produced by a facile and low-energy-intensive molten salt route using MoS2 and NaCl as precursors. The solubility of the Na2Mo2O7 product in water is confirmed by assessing the light absorption of the dissolved substance. The solubility values change between around 0.4 to 3.0 g l−1, depending on the temperature and pH level. The Na-ion storage performance of the molten salt-produced Na2Mo2O7 is characterized by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy tests. Nanostructuring of Na2Mo2O7 through high-energy ball milling with graphene nanosheets decreases the interface impedance, enhancing the pseudocapacitive performance of the material.

Bimetallic nickel cobalt sulfides with hierarchical coralliform architecture for ultrafast and stable Na-ion storage

A series of bimetallic nickel cobalt sulfides with hierarchical micro/nano architectures were fabricated via a facile synthesis strategy of bimetallic micro/nano structure precursor construction-anion exchange via solvothermal method. Among the nickel cobalt sulfides with different Ni/Co contents, the coral-like Ni1.01Co1.99S4 (Ni/Co, 1/2) delivers ultrafast and stable Na-ion storage performance (350 mAh·g−1 after 1,000 cycles at 1 A·g−1 and 355 mAh·g−1 at 5 A·g−1). The remarkable electrochemical properties can be attributed to the enhanced conductivity by co-existence of bimetallic components, the unique coral-like micro/nanostructure, which could prevent structural collapse and self-aggregation of nanoparticles, and the easily accessibility of electrolyte, and fast Na+ diffusion upon cycling. Detailed kinetics studies by a galvanostatic intermittent titration technique (GITT) reveal the dynamic change of Na+ diffusion upon cycling, and quantitative kinetic analysis indicates the high contribution of pseudocapacitive behavior during charge-discharge processes. Moreover, the ex-situ characterization analysis results further verify the Na-ion storage mechanism based on conversion reaction. This study is expected to provide a feasible design strategy for the bimetallic sulfides materials toward high performance sodium-ion batteries.

Antiblocking Heterostructure to Accelerate Kinetic Process for Na-Ion Storage.

Heterostructures are attracting increasing attention in the field of sodium-ion batteries. However, it is still unclear whether any two monophase components can be used to construct a high-performance heterostructure for sodium-ion batteries, as well as the kind of heterostructures that can boost electrochemical performances. In this study, based on classical semiconductor theories on antiblocking and blocking interfaces, attempts are made to answer the abovementioned queries. For this purpose, NiTe2 -ZnTe antiblocking and CoTe2 -ZnTe blocking heterostructures are synthesized through a bimetal-hexamine framework-derived strategy. The NiTe2 -ZnTe antiblocking heterostructure exhibits excellent high-rate and cycling performances, while the CoTe2 -ZnTe blocking heterostructure performs poorly, even compared to their monophase components. Further, kinetic measurements and theoretical calculation confirm that antiblocking heterointerfaces can boost Na-ion diffusion efficiency and decrease the diffusion barrier, which can be attributed to the highly conductive antiblocking heterointerfaces generated due to electron transfer from NiTe2 to ZnTe. Therefore, this study provides a new perspective to design heterostructures more efficiently, with significantly better Na-ion storage performance.

Effect of Vinylene Carbonate Electrolyte Additive on the Surface Chemistry and Pseudocapacitive Sodium-Ion Storage of TiO2 Nanosheet Anodes

Although titanium dioxide has gained much attention as a sodium-ion battery anode material, obtaining high specific capacity and cycling stability remains a challenge. Herein, we report significantly improved surface chemistry and pseudocapacitive Na-ion storage performance of TiO2 nanosheet anode in vinylene carbonate (VC)-containing electrolyte solution. In addition to the excellent pseudocapacitance (~87%), the TiO2 anodes also exhibited increased high-specific capacity (219 mAh/g), rate performance (40 mAh/g @ 1 A/g), coulombic efficiency (~100%), and cycling stability (~90% after 750 cycles). Spectroscopic and microscopic studies confirmed polycarbonate based solid electrolyte interface (SEI) formation in VC-containing electrolyte solution. The superior electrochemical performance of the TiO2 nanosheet anode in VC-containing electrolyte solution is credited to the improved pseudocapacitive Na-ion diffusion through the polycarbonate based SEI (coefficients of 1.65 × 10−14 for PC-VC vs. 6.42 × 10−16 for PC). This study emphasizes the crucial role of the electrolyte solution and electrode–electrolyte interfaces in the improved pseudocapacitive Na-ion storage performance of TiO2 anodes.

Growth of carbon nanofibers through chemical vapor deposition for enhanced sodium ion storage

Innovation of carbon anodes plays a significant role in the commercialization of Sodium-ion batteries. In this work, we report hybrid carbon nanofibers synthesized by a facile chemical vapor deposition method and explore their application potential as anode for sodium ion storage. The designed hybrid carbon nanofibers have diameters of 50−150 nm and show linear and spiral structures. Impressively, the carbon nanofibers anode exhibits good electrochemical performance with a high initial Coulombic efficiency of 87.6 % and excellent cycling stability with a capacity retention of 75.4 % at the 100th cycle. The improved Na-ion storage performance is attributed to the carbon nanofiber structure with considerable defect concentration and shortened transfer length for ions and electrons. Moreover, the fibrous structure is interconnected with cross-linked pores, contributing to good mechanical stability and reduced contact resistance. Our work may provide valuable inspiration for developing advanced electrodes for advanced alkali ion energy storage.

Citrate-mediated synthesis of highly crystalline transition metal hexacyanoferrates and their Na ion storage properties

In this work, highly crystalline transition-metal hexacyanoferrates (MHCFs) have been synthesized in the presence of citrate, which is found not only to mediate the precipitation reaction rate but also prevent the MHCF crystals from aggregation. This method is applicable to a wide range of MHCFs with different transition metals (e.g., Co, Ni, Mn and Zn). The highly crystalline MHCFs with little Fe(CN)6 vacancies and rich alkaline ions exhibited significantly improved electrochemical performance for Na ion storage in both aqueous and organic electrolytes. The effect of transition metals in MHCFs on the Na ion storage performance has been investigated in an aqueous electrolyte. Results showed that the CoHCF nanocube sample displayed the highest electrochemical performance than other MHCFs samples synthesized in this work. This CoHCF sample exhibits a specific capacity of 85 mAh g−1 at 1 A g−1. The CoHCF sample also displays a good cycling stability with capacity retentions of 92% after 12,000 cycles in aqueous electrolyte (0.5 M Na2SO4) and 78% after 10,000 cycles in organic electrolyte (NaClO4 in PC + EC with 5% FEC).

Ultrathin 2D FexCo1-xSe2 nanosheets with enhanced sodium-ion storage performance induced by heteroatom doping effect

Exploring simple synthesis method of high-performance sodium-ion batteries (SIBs) electrode materials has always been highly concerned in large-scale energy storage technology filed. Here, ultrathin two-dimensional (2D) FexCo1-xSe2 nanosheets as anode material for SIBs are successfully synthesized by one-step solvothermal method. The average thickness of Fe0·08Co0·92Se2 nanosheets is approximately 3.08 nm, which is about equivalent to the thickness of six b-axis crystal cells. When employed as anode for SIBs, Fe0·08Co0·92Se2 nanosheets display a high initial discharge specific capacity of 679.8 mAh/g, a high initial coulombic efficiency of 85.5% and superior reversible specific capacity of 510.4 mAh/g at 1 A/g. Simultaneously, Fe0·08Co0·92Se2 also exhibits an enhanced rate capability (480.0, 460.0, 435.1 mAh/g at 0.2, 2, 4 A/g respectively) and outstanding cycling stability at relatively large current density (397.0 mAh/g at 4 A/g after 1000 cycles). The excellent Na-ion storage performance of FexCo1-xSe2 nanosheets could be ascribed to the abundant electrochemical active sites and shorten ion transfer tunnels provided by this ultrathin 2D structure and bimetallic ion synergistic effect by heteroatom doping. Noticeably, the capacitive contribution may play the key role in the admirable rate capability through electrochemical kinetics analysis of Fe0·08Co0·92Se2 nanosheets. Therefore, this work presents a simple preparation of ultrathin 2D selenide nanosheets and an effective low-cost regulation strategy for improving Na-ion storage performance.