Practical Application Of Sodium-ion Batteries Research Articles

Hierarchical Octahedra Constructed by Cu2 S/MoS2 ⊂Carbon Framework with Enhanced Sodium Storage.

Metal sulfides have aroused considerable attention for efficient sodium storage because of their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium-ion batteries. Herein, a self-template-based strategy is designed to controllably synthesize hierarchical microoctahedra assembled with Cu2 S/MoS2 heterojunction nanosheets in the porous carbon framework (Cu2 S/MoS2 ⊂PCF) via a facile coprecipitation method coupled with vulcanization treatment. The Cu2 S/MoS2 ⊂PCF microoctahedra with 2D hybrid nanosubunits reasonably integrate several merits including facilitating the diffusion of electrons and Na+ ions, enhancing the electric conductivity, accelerating the ion and charge transfer, and buffering the volume variation. Therefore, the Cu2 S/MoS2 ⊂PCF composite manifests efficient sodium storage performance with high capacity, long cycling life, and excellent rate capability.

Synthesis of CuS@CoS2 Double-Shelled Nanoboxes with Enhanced Sodium Storage Properties.

Metal sulfides have received considerable attention for efficient sodium storage owing to their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium-ion batteries. Herein, an elegant multi-step templating strategy has been developed to rationally synthesize hierarchical double-shelled nanoboxes with the CoS2 nanosheet-constructed outer shell supported on the CuS inner shell. Their structure and composition enable these hierarchical CuS@CoS2 nanoboxes to show boosted electrochemical properties with high capacity, outstanding rate capability, and long cycle life.

In situ visualization of sodium transport and conversion reactions of FeS2 nanotubes made by morphology engineering

Iron disulfide (FeS2), existing in nature as pyrite, holds great promise as a conversion-type anode material for sodium-ion batteries (SIBs), owing to its low cost and high theoretical capacity. However, the large volume expansion and the sluggish electrode reaction kinetics during conversion reactions impede its large-scale practical application in SIBs. Here, we demonstrate the utilization of morphological engineering to achieve poly-crystalline FeS2 nanotubes (NTs) consisting of tiny FeS2 crystallites. In situ transmission electron microscopy observations reveal that 1D shape can afford straight pathways for Na transport to expedite reaction kinetics, and poly-crystalline structure can buffer large volume expansion and structural strain. Furthermore, high-resolution imaging and electron diffraction were utilized to track phase evolution associated with conversion reactions in real time. We have identified an intercalation-conversion reaction mechanism from the FeS2 phase to the Na2S + Fe phases via the intermediate NaFeS2 phase upon initial sodiation. Impressively, a reversible and symmetric conversion reaction between NaFeS2 phase and Na2S + Fe phases is established during subsequent sodiation−desodiation cycles. Notably, this is the first report of FeS2 NTs investigated for secondary battery electrode material. This work not only provides valuable insights into sodium storage mechanism of FeS2 material, but also corroborates the pivotal role of morphology engineering in optimizing the microstructure of electrode materials for advanced SIBs.

Understanding the influence of different carbon matrix on the electrochemical performance of Na3V2(PO4)3 cathode for sodium-ion batteries

Na-superionic conductor-structured Na3V2(PO4)3 is extensively investigated as a promising cathode material for sodium-ion batteries. Unfortunately, the Na3V2(PO4)3 cathode suffers from low rate capability due to its inherent low electric conductivity. One of the general solutions to this dilemma is to embed the Na3V2(PO4)3 nanoparticles uniformly within carbon matrix, however, the effect of carbon matrix categories on the sodium storage performance of Na3V2(PO4)3 is unclear. Here we systematically compare the influence of different carbon matrix on the electrochemical properties of the Na3V2(PO4)3 cathode and find that expanded graphite outperforms carbon nanotubes and carbon black as carbon matrix. As a result, the as-synthesized Na3V2(PO4)3/expanded graphite composite delivers a high reversible capacity of 111.4 mAh g−1 at 1C, superior rate capability (105 mAh g−1 at 50C), and ultralong cycle life (48 mAh g−1 after 20,000 cycles at 50C), which are better than most Na3V2(PO4)3-based composites reported previously. Moreover, the remarkable electrochemical performance of Na3V2(PO4)3/expanded graphite in symmetric cells further advances the practical application of sodium-ion batteries.

A Multi-Ion Strategy towards Rechargeable Sodium-Ion Full Batteries with High Working Voltage and Rate Capability.

Sodium-ion batteries (SIBs) are a promising alternative for the large-scale energy storage owing to the natural abundance of sodium. However, the practical application of SIBs is still hindered by the low working voltage, poor rate performance, and insufficient cycling stability. A sodium-ion based full battery using a multi-ion design is now presented. The optimized full batteries delivered a high working voltage of about 4.0 V, which is the best result of reported sodium-ion full batteries. Moreover, this multi-ion battery exhibited good rate performance up to 30 C and a high capacity retention of 95 % over 500 cycles at 5 C. Although the electrochemical performance of this multi-ion battery may be further enhanced via optimizing electrolyte and electrode materials for example, the results presented clearly indicate the feasibility of this multi-ion strategy to improve the electrochemical performance of SIBs for possible energy storage applications.

3D Interconnected MoS2 with Enlarged Interlayer Spacing Grown on Carbon Nanofibers as a Flexible Anode Toward Superior Sodium-Ion Batteries

Molybdenum disulfide (MoS2) has attracted extensive research interest as a fascinating anode for sodium-ion batteries (SIBs) because of its high specific capacity of 670 mA h g-1. However, unsatisfied cycling durability and poor rate performance are two barriers that hinder MoS2 for practical application in SIBs. Herein, 3D interconnected MoS2 with enlarged interlayer spacing epitaxially grown on 1D electrospinning carbon nanofibers (denoted as MoS2@CNFs) was prepared as a flexible anode for SIBs via l-cysteine-assisted hydrothermal method. Benefitting from the C-O-Mo bonding between the CNFs and MoS2 as well as the rational design with novel structure, including the well-retained 3D interconnected and conductive MoS2@CNFs networks and expanded (002) plane interlayer space, the flexible MoS2@CNFs electrode achieves a remarkable specific capacity (528 mA h g-1 at 100 mA g-1), superior rate performance (412 mA h g-1 at 1 A g-1), and ultralong cycle life (over 600 cycles at 1 A g-1 with excellent Coulombic efficiencies exceeding 99%). The elaborate strategy developed in this work opens a new avenue to prepare highly improved energy storage materials, especially suitable for flexible electronics.

Cross-Linking Hollow Carbon Sheet Encapsulated CuP2 Nanocomposites for High Energy Density Sodium-Ion Batteries.

Sodium-ion batteries (SIB) are regarded as the most promising competitors to lithium-ion batteries in spite of expected electrochemical disadvantages. Here a "cross-linking" strategy is proposed to mitigate the typical SIB problems. We present a SIB full battery that exhibits a working potential of 3.3 V and an energy density of 180 Wh kg-1 with good cycle life. The anode is composed of cross-linking hollow carbon sheet encapsulated CuP2 nanoparticles (CHCS-CuP2) and a cathode of carbon coated Na3V2(PO4)2F3 (C-NVPF). For the preparation of the CHCS-CuP2 nanocomposites, we develop an in situ phosphorization approach, which is superior to mechanical mixing. Such CHCS-CuP2 nanocomposites deliver a high reversible capacity of 451 mAh g-1 at 80 mA g-1, showing an excellent capacity retention ratio of 91% in 200 cycles together with good rate capability and stable cycling performance. Post mortem analysis reveals that the cross-linking hollow carbon sheet structure as well as the initially formed SEI layers are well preserved. Moreover, the inner electrochemical resistances do not significantly change. We believe that the presented battery system provides significant progress regarding practical application of SIB.

Porous NaTi2(PO4)3/C Hierarchical Nanofibers for Ultrafast Electrochemical Energy Storage.

NaTi2(PO4)3 (NTP) with a sodium superionic conductor three-dimensional (3D) framework is a promising anode material for sodium-ion batteries (SIBs) because of its suitable potential and stable structure. Although its 3D structure enables high Na-ion diffusivity, low electronic conductivity severely limits NTP's practical application in SIBs. Herein, we report porous NTP/C nanofibers (NTP/C-NFs) obtained via an electrospinning method. The NTP/C-NFs exhibit a high reversible capacity (120 mA h g-1 at 0.2 C) and a long cycling stability (a capacity retention of ∼93% after 700 cycles at 2 C). Furthermore, sodium-ion full cells and hybrid sodium-ion capacitors have also been successfully assembled, both of which exhibit high-rate capabilities and remarkable cycling stabilities because of the high electronic/ionic conductivity and impressive structural stability of NTP/C-NFs. The results show that the nanoscale-tailored NTP/C-NFs could deliver new insights into the design of high-performing and highly stable anode materials for room-temperature SIBs.

Application of materials based on group VB elements in sodium-ion batteries: A review

Owing to their high redox activity, abundant resource, and low cost, compounds based on group VB elements (V, Nb, and Ta) are promising electrode materials for an array of energy storage devices. Moreover, their open structure benefits transportation and accommodation of alkali Na+ ions, rending them particularly appealing for cost-effective sodium-ion batteries (SIBs). In the last decade, these materials have evoked intensive investigations in SIBs, serving as either cathode, anode, or both depending on their sodiation degree and redox potential. Exciting progress has been made, but significant gaps in our knowledge still remain. Their practical application in SIBs remains unclear and thus calls for further efforts to settle several technical challenges in terms of poor conductivity, unstable cycling, and inefficient charge storage. In this perspective, a brief overview is given of recent progress on how to solve these technical issues and envision their bright future in SIBs, which may serve as a source to inspire researches on relevant topics.

High-capacity FeTiO3/C negative electrode for sodium-ion batteries with ultralong cycle life

The development of electrode materials which improve both the energy density and cycle life is one of the most challenging issues facing the practical application of sodium-ion batteries today. In this work, FeTiO3/C nanoparticles are synthesized as negative electrode materials for sodium-ion batteries. The electrochemical performance and charge-discharge mechanism of the FeTiO3/C negative electrode are investigated in an ionic liquid electrolyte at 90 °C. The FeTiO3/C negative electrode delivers a high reversible capacity of 403 mAh g−1 at a current rate of 10 mA g−1, and exhibits high rate capability and excellent cycling stability for up to 2000 cycles. The results indicate that FeTiO3/C is a promising negative electrode material for sodium-ion batteries.

General One-Pot Synthesis of Transition-Metal Phosphide/Nitrogen-Doped Carbon Hybrid Nanosheets as Ultrastable Anodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have been considered as promising energy storage devices in grid-level applications, owing to their largely reduced cost compared with that of lithium-ion batteries. However, the practical application of SIBs has been seriously hindered because of the lack of appropriate anode materials, limited by the thermodynamics perspective, which is one of the central task at current stage. Herein, we have developed a general one-pot strategy for the synthesis of transition-metal phosphide (TMP) based hybrid nanosheets composed of carbon-coated TMP nanoparticles anchored to the surface of nitrogen-doped carbon nanosheets. This facile and cost-effective method is quite universal and holds potential to be further extended to other metal phosphide materials. Significantly, the hybrid nanosheet electrode possesses excellent sodium storage properties as anodes for SIBs, including high specific capacity, an ultra-long cycle life and a remarkable rate performance. This work makes a significant contribution to not only the synthetic methodology of TMP-carbon two-dimensional hybrid nanostructures, but also the application of TMP-based anodes for high-energy SIBs.

Alkaline earth metal vanadates as sodium-ion battery anodes

The abundance of sodium resources indicates the potential of sodium-ion batteries as emerging energy storage devices. However, the practical application of sodium-ion batteries is hindered by the limited electrochemical performance of electrode materials, especially at the anode side. Here, we identify alkaline earth metal vanadates as promising anodes for sodium-ion batteries. The prepared calcium vanadate nanowires possess intrinsically high electronic conductivity (> 100 S cm−1), small volume change (< 10%), and a self-preserving effect, which results in a superior cycling and rate performance and an applicable reversible capacity (> 300 mAh g−1), with an average voltage of ∼1.0 V. The specific sodium-storage mechanism, beyond the conventional intercalation or conversion reaction, is demonstrated through in situ and ex situ characterizations and theoretical calculations. This work explores alkaline earth metal vanadates for sodium-ion battery anodes and may open a direction for energy storage.

Self-Assembled CoS Nanoflowers Wrapped in Reduced Graphene Oxides as the High-Performance Anode Materials for Sodium-Ion Batteries.

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.