Improved Sodium Storage Research Articles

Controllable Orientation of MoSe2 Nanosheets Anchored on Carbon Cloth as Self-Supporting Anodes for Improved Sodium Storage Performance

It is an important strategy to improve the sodium storage performance by using carbon cloth to support the active material. However, the effect of structural changes of active materials anchored on the surface of carbon cloth on sodium storage performance remains to be further studied. In this work, we control MoSe2 morphology on the surface of carbon cloth via annealing conditions. Under different annealing conditions, MoSe2 shows vertical, tilted and horizontal morphology on the surface of carbon cloth. When used as anode materials for sodium ion storage, the tilted-orientation MoSe2 composite electrode shows the best sodium storage performance, achieving a high cycling capacity of 253 mA h g−1 after 200 cycles at 1 A g−1 and excellent rate performance of 140.5 mA h g−1 at 5.0 A g−1. The excellent performance is related to the orientation of MoSe2 on carbon cloth. The tilted-orientation MoSe2/CC(carbon cloth) has hierarchical two-dimensional nanosheets structure and strong interface contact, which can prevent the self-aggregation of active material and keep well contact between MoSe2 nanosheets with carbon cloth. This work provides a reference to improve sodium storage performance for two-dimensional layered transition-metal dichalcogenides.

Advanced sodium storage properties of a porous nitrogen-doped carbon with a NiO/Cu/Cu2O hetero-interface derived from bimetal–organic frameworks

We designed an excellent-performance porous nitrogen-doped carbon material with a NiO/Cu/Cu2O hetero-interface derived from bimetal-organic frameworks. The hetero-interfaces between NiO/Cu/Cu2O could boost the Na+ diffusion and increase the electrical conductivity. The obtained composite achieves highly reversible Na-storage with excellent cycling stability and rate capability.

Effect of Vapor Carbon Coating on the Surface Structure and Sodium Storage Performance of Hard Carbon Spheres

Hard carbons have received considerable attention as anode materials for sodium‐ion batteries (SIBs). However, it is still a challenge to improve the plateau capacity and initial coulombic efficiency (ICE) of hard carbons. Herein, a facile vapor carbon‐coating method is used to modify the surface structure of carbon spheres (CS) via the pyrolysis of polypropylene (PP), aiming to seal the exposed pores through a high‐quality carbon layer. CS@2%PP exhibits highly improved sodium storage performance compared to that of the pristine CS, which delivers a plateau capacity of 220 m Ah g−1 and an ICE of 81%. Further investigations show that the improved sodium storage performance of CS@2%PP can be mainly attributed to the reduced structural defects on the surface, lower specific surface area (11.5 m2 g−1), and increased closed pores (12.5%) via carbon coating. The results prove that the surface vapor carbon coating is a facile route to improve the plateau capacity and ICE of hard carbon anodes in SIBs.

N/S-Co-Doped Porous Carbon Sheets Derived from Bagasse as High-Performance Anode Materials for Sodium-Ion Batteries.

Heteroatom doping is considered to be an efficient strategy to improve the electrochemical performance of carbon-based anode materials for Na-ion batteries (SIBs), due to the introduction of an unbalanced electron atmosphere and increased electrochemical reactive sites of carbon. However, developing green and low-cost approaches to synthesize heteroatom dual-doped carbon with an appropriate porous structure, is still challenging. Here, N/S-co-doped porous carbon sheets, with a main pore size, in the range 1.8–10 nm, has been fabricated through a simple thermal treatment method, using KOH-treated waste bagasse, as a carbon source, and thiourea, as the N and S precursor. The N/S-co-doped carbon sheet electrodes possess significant defects, high specific surface area, enhanced electronic conductivity, improved sodium storage capacity, and long-term cyclability, thereby delivering a high capacity of 223 mA h g−1 at 0.2 A g−1 after 500 cycles and retaining 155 mA h g−1 at 1 A g−1 for 2000 cycles. This work provides a low-cost route to fabricate high-performance dual-doped porous carbonaceous anode materials for SIBs.

High nitrogen doped carbon nanofiber aerogels for sodium ion batteries: synergy of vacancy defects to boost sodium ion storage

The electrochemical performance of sodium ion batteries (SIBs) may be enhanced through improving current carbonaceous materials. These materials exhibit the inferior sodium storage performance due to the limited interlayer spacing and Na+ intercalation. We report an approach for preparing porous nitrogen-doped carbon nanofiber (20 nm diameter) aerogels with large-size defect structures and the high N content derived from chitin. When the aerogels were utilized as the anode material for SIBs, the sample showed the high reversible capacity of 282 mA h g−1 at 0.1 A g−1, the satisfactory rate capability of 175 mA h g−1 at 5 A g−1 and the super cycling stability (249 mA h g−1 at 0.5 A g−1 over 7000 cycles). According to the computation results of density functional theory (DFT), the optimally enhanced electrochemical performance of N-doped material for SIB anodes was ascribed to the synergistic effect of defect structures and N-doping, thus providing the theoretical basis of the complementary relationship between the improved sodium storage performance and structural defects in the carbon framework.

Facile synthesis of SnSe2 nanoparticles supported on graphite nanosheets for improved sodium storage and hydrogen evolution

SnSe2 attract enormous attention in sodium-ion batteries since it has a high theoretical specific capacity of 756 mAh g−1. However, the large volume expansion of SnSe2 during Na+ insertion/extraction processes seriously affects the cyclic stability of SnSe2-based electrodes. Herein, 5 nm SnSe2 nanoparticles supported on the graphite nanosheets are synthesized by two-step high-energy ball milling to obtain SnSe2/graphite nanosheet nanocomposite. By virtue of the ultrafine SnSe2 nanoparticles and the porous carbon skeleton constructed by highly conductive graphite nanosheets, the as-obtained SnSe2/graphite nanosheet nanocomposite presents a high specific capacity of 638.6 mAh g−1 at 200 mA g−1, excellent rate capacity of 517.8 mAh g−1 at 5 A g−1, and ultralong cyclic life (252.9 mAh g−1 after 4000 cycles at 2 A g−1), which are superior to the previously reported SnSe2-based composites. Ex-situ X-ray diffraction, Raman mapping, high-resolution transmission electron microscope, and X-ray photoelectron spectroscopy characterizations show that the crystal structure of SnSe2 is reversible during sodium ions insertion/extraction processes and the distribution of SnSe2 nanoparticles on graphite nanosheets remains uniform. Moreover, this nanocomposite can not only be used as a high-performance anode for sodium-ion full cells, but also as an improved electrocatalyst for hydrogen evolution reaction.

Extended lattice space of TiO2 hollow nanocubes for improved sodium storage

Sodium-ion batteries (SIBs) are considered as promising new-fashioned energy storage devices. Among these anode materials of SIBs, the low specific capacity and poor rate capability of TiO2 are two significant factors of hindering the widely application. Here, a unique hollow TiO2/carbon nanocubes (hollow-TiO2@C-800) with enlarged lattice spacing of TiO2 have been synthesized. Experimental results demonstrate that the enlarged lattice spacing of TiO2 could facilitate Na ions desertion/insertion and inhibit the irreversible side reactions, resulting in fast Na ion transfer kinetics. Moreover, N-doped hollow porous carbon framework could boost the conductivity, inhibit the agglomeration of the smaller TiO2 and shorten the distance for Na+ transfer, which lead to lower mechanical stresses and smaller capacity loss during cycles. As expected, hollow-TiO2@C-800 shows a superior cycling stability (154.6 mAh g−1 after 6000 cycles at 5000 mA g−1) and an excellent rate capability (150 mAh g−1 at 8000 mA g−1). This simple synthetic method would open a new avenue to prepare the superior SIBs anode.

Metal-organic framework derived 3D graphene decorated NaTi2(PO4)3 for fast Na-ion storage.

NASCION-type materials featuring super ionic conductivity are of considerable interest for energy storage in sodium ion batteries. However, the issue of inherent poor electronic conductivity of these materials represents a fundamental limitation in their utilization as battery electrodes. Here, for the first time, we develop a facile strategy for the synthesis of NASICON-type NaTi2(PO4)3/reduced graphene oxide (NTP-rGO) Na-ion anode materials from three-dimensional (3D) metal-organic frameworks (MOFs). The selected MOF serves as an in situ etching template for the titanium resource, and importantly, endows the materials with structure-directing properties for the self-assembly of graphene oxide (GO) through a one-step solvothermal process. Through the subsequent carbonization, an rGO decorated NTP architecture is obtained, which offers fast electron transfer and improved Na+ ion accessibility to active sites. Benefiting from its unique structural merits, the NTP-rGO exhibits improved sodium storage properties in terms of high capacity, excellent rate performance and good cycling life. We believe that the findings of this work provide new opportunities to design high performance NASICON-type materials for energy storage.

The dual-function sacrificing template directed formation of MoS2/C hybrid nanotubes enabling highly stable and ultrafast sodium storage

A unique dual-function sacrificing template directed strategy was developed to synthesize MoS2/carbon hybrid nanotubes, achieving greatly improved sodium storage performance.

Revealing the atomistic origin of the disorder-enhanced Na-storage performance in NaFePO4 battery cathode

Among the various types of cathode materials for sodium ion batteries, NaFePO4 attracts much attention owing to its high theoretical capacity (155 mA h g−1), low cost, high structural stability, and non-toxicity. Nevertheless, the NaFePO4 with maricite structure, thermodynamically stable phase, has been considered as electrochemically inactive for sodium-ion storage. In this work, we succeeded in tuning the degree of disorder in NaFePO4 cathode material by a mechanochemical route to enhance electrochemical performances of Na-ion batteries. The derived NaFePO4 cathodes containing both amorphous and maricite phases exhibit much improved sodium storage performance with an initial capacity of 115 mA h g−1 at 1 C and an excellent cycling stability of capacity retention of 91.3% after 800 cycles. By X-ray absorption near edge and Raman spectroscopy, we revealed the atom-scale structural origin of the enhanced Na-storage performances of the amorphous NaFePO4 electrode. The transformation of edge-sharing FeO6 octahedra into various FeOn polyhedra upon amorphization was found to be a key to attain the superior performances for Na ion batteries.

Improved sodium storage performances of plasma treated self-supported carbon fibers

Sodium-ion batteries have been widely considered as promising energy storage systems due to the abundance and low cost of sodium. However, to find a kind of anode material with appropriate sodium storage and high structural stability still remains challenging. In this work, self-supported porous carbon fibers were prepared by electrospinning technique and plasma treatments. It's found that the porous carbon fibers become more loose after the plasma treatments, and the surface compositions are changed. Results show that the material after plasma treatments could deliver capacities higher than 200 mAh/g when the current density is 1000 mA/g. EIS results show that the charge transfer resistances of the treated material keep more stable after electrochemical cycles. And these improvements may be results of the plasma treatments. Detailed mechanisms are studied in this research.

Two-step carbon modification of NaTi2(PO4)3 with improved sodium storage performance for Na-ion batteries

NASICON-type structured NaTi2(PO4)3 has been regarded as a promising anode material for non-aqueous and aqueous Na-ion batteries, whereas its sodium storage performance was greatly restricted by its inherent inferior electronic conductivity. In the present work, a two-step carbon modification method using prefabricated carbon spheres as support and phenolic resin as carbon source was proposed to prepare advanced NaTi2(PO4)3/C. The as-prepared composite with carbon spheres displayed a much higher reversible capacity (126.7 mA·h/g vs 106.7 mA·h/g at 0.5C) than the control sample without carbon spheres. Superior rate capability with discharge capacities of 115.1, 95.5, 80.8 mAh/g at 1C, 10C, 20C, respectively and long-term cycling stability with capacity retention of 92.4% after 1000 cycles at 5C were also observed. Owing to the designing of two-step carbon modification, although the as-prepared sample shows much smaller surface area, it possesses much better conductive network and more uniform particle distribution, resulting in higher electronic conductivity and faster ionic conductivity, thereby superior sodium storage ability at high rate.

A Flexible Sulfur-Enriched Nitrogen Doped Multichannel Hollow Carbon Nanofibers Film for High Performance Sodium Storage.

Heteroatom doping is regarded as a promising method to enhance the sodium storage performance of carbon materials. In this work, a sulfur-enriched N-doped multichannel hollow carbon nanofiber (denoted as S-NCNF) film is prepared through electrospinning technology and heat treatment with sublimed sulfur as the flexible anode for sodium ion batteries (NIBs). The S-NCNF film displays outstanding electrochemical performance, particularly with a high rate capacity (132 mA h g-1 at the current density of 10 A g-1 ) and remarkable long cycling stability (reversible specific capacity of 187 mA h g-1 at 2 A g-1 over 2000 cycles). The improved sodium storage performance results from the unique 3D structure, abundant defects, and increased interlayer spacing of S-NCNFs. The density functional theory calculations demonstrate that nitrogenous carbon nanofibers doping with sulfur could not only promote the adsorption of sodium but also favor electrons' transfer. This strategy has been demonstrated as a general process to design free-standing carbon-based thin film with other heteroatom doping.

Tailoring graphitic nanostructures in hard carbons as anode materials achieving efficient and ultrafast sodium storage

Hard carbons appear to be promising anode candidates in high-performance sodium-ion batteries (SIBs) for large-scale stationary energy storage due to their large interlayer distance and amorphous structure, which facilitate sodium ions insertion/desertion. However, several major hurdles to address are poor rate performances and the low initial coulombic efficiency (ICE). Herein, a facile strategy to tailor hard carbons with graphitic nanostructures and rational specific surface area is proposed to improve sodium storage. Resin-derived carbon nanobroccolis (CNB) with in situ decorated graphitic nanostructures have been successfully synthesized by self-assembly and low-temperature catalytic carbonization process. As a result, attribute to in situ tailored graphitic nanostructures in hard carbons and rational specific surface area, CNB electrodes possess less charge transfer resistance and excellent sodium ions diffusion kinetics and successfully achieve fast and efficient sodium storage. When used as anode for sodium-ion batteries, CNB electrodes exhibit excellent high-rate capability of 137 mAh g−1 at 1000 mA g−1 and enhanced ICE of 52.6%. Our strategy reported here opens a door to design high-performance carbon anode materials for SIBs particularly focusing on efficient sodium ions storage and fast sodium ions diffusion.

Metal-Organic Frameworks-Derived Co2P@N-C@rGO with Dual Protection Layers for Improved Sodium Storage.

The Co2P nanoparticles hybridized with unique N-doping carbon matrices have been successfully designed employing ZIF-67 as the precursor via a facile two-step procedure. The Co2P nanostructures are shielded with reduced graphene oxide (rGO) to enhance electrical conductivity and mitigate volume expansion/shrinkage during sodium storage. As anode materials for sodium-ion batteries (SIBs), the novel architectures of Co2P@N-C@rGO exhibited excellent sodium storage performance with a high reversible capacity of 225 mA h g-1 at 50 mA g-1 after 100 cycles. Our study demonstrates the significant potential of Co2P@N-C@rGO as anode materials for SIBs.

Enhanced sodium storage performance in flexible free-standing multichannel carbon nanofibers with enlarged interlayer spacing

A flexible and free-standing multichannel carbon nanofiber (MCNF) film electrode was fabricated through electrospinning and carbonization. After high-temperature treatment of MCNFs in vacuum, the obtained fibers (MCNFs-V) had a dilated interlayer spacing of graphene sheets (0.398 nm) and an ultra-low specific surface area (15.3 m2/g). When used as an anode for sodium-ion batteries, the MCNFs-V showed a discharge plateau below 0.1 V, and sodium was intercalated into the stacked graphene sheets layers during the sodiation process. The MCNFs-V exhibited a reversible and high specific capacity of 222 mAh/g at a current density of 0.1 A/g after 100 cycles and excellent long-term cycling stability, which was superior to that of MCNFs. The improved sodium storage performance was attributed to the unique microstructure of the MCNFs-V with an enlarged interlayer spacing of graphene sheets for sodium intercalation. The MCNFs-V electrode holds great promise as an anode material for commercial sodium-ion batteries.

Binding Sulfur‐Doped Nb2O5 Hollow Nanospheres on Sulfur‐Doped Graphene Networks for Highly Reversible Sodium Storage

AbstractOrthorhombic Nb2O5 (T‐Nb2O5) has recently attracted great attention for its application as an anode for sodium ion batteries (NIBs) owing to its patulous framework and larger interplanar lattice spacing. Sulfur‐doped T‐Nb2O5 hollow nanospheres (diameter:180 nm) uniformly encapsulate into sulfur‐doped graphene networks (denoted: S‐Nb2O5 HNS@S‐rGO) using hard template method. The 3D ordered porous structure not only provides good electronic transportation path but also offers outstanding ionic conductive channels, leading to an improved sodium storage performance. In addition, the introduction of sulfur to graphene and Nb2O5 leads to oxygen vacancy and enhanced electronic conductivity. The sodium storage performance of S‐Nb2O5 HNS@S‐rGO is unprecedented. It delivers a reversible capacity 215 mAh g−1 at 0.5 C over 100 cycles. In addition, it also possesses a great high‐rate capability, retaining a stable capacity of 100 mAh g−1 at 20 C after 3000 cycles. This design demonstrates the potential applications of Nb2O5 as anode for high performance NIBs.

Plasma-Induced Oxygen Vacancies in Urchin-Like Anatase Titania Coated by Carbon for Excellent Sodium-Ion Battery Anodes.

The incorporation of oxygen vacancies in anatase TiO2 has been studied as a promising way to accelerate the transport of electrons and Na+ ions, which is important for achieving excellent electrochemical properties for anatase TiO2. However, wittingly introducing oxygen vacancies in anatase TiO2 for sodium-ion anodes by a facile and effective method is still a challenge. In this work, we report an innovative method to introduce oxygen vacancies into the urchin-like N-doped carbon coated anatase TiO2 (NC-DTO) by a facile plasma treatment. The superiorities of the oxygen vacancies combined with the conductive N-doped carbon coating enable the obtained NC-DTO of greatly improved sodium storage performance. When served as the anode for sodium-ion batteries, the NC-DTO electrode shows superior electrochemical performance (capacity: 272 mA h g-1 at 0.25 C, capacity retention: 98.8% after 5000 cycles at 10 C, as well as ultrahigh capacity: 150 mA h g-1 at 15 C). Density functional theory calculations combined with experimental results suggest that considerably improved sodium storage performance of NC-DTO is due to the enhanced electronic conductivity from the N-doped carbon layer as well as narrowed band gap and lowered sodiation energy barrier from the introduction of oxygen vacancies. This work highlights that introducing oxygen vacancies into TiO2 by plasma is a promising method to enhance the electrochemical property of TiO2, which also can be applied to different metal oxides for energy storage devices.

Confining SnS2 Ultrathin Nanosheets in Hollow Carbon Nanostructures for Efficient Capacitive Sodium Storage

Summary Tin disulfide (SnS 2 ) is a promising anode material for sodium-ion batteries because of its high specific capacity. However, the low conductivity and large volume change during reaction with Na + ions greatly limit its practical application. Herein, a multistep templating method has been exploited for the rational design and synthesis of SnS 2 nanosheets confined in carbon nanotubes (SnS 2 @CNTs). To demonstrate the universality of this method, SnS 2 nanosheets confined in carbon nanoboxes (SnS 2 @CNBs) and hollow carbon nanospheres (SnS 2 @CNSs) have also been synthesized by simply changing the template in the reaction system. Due to their unique structural merits, the SnS 2 @CNTs, SnS 2 @CNBs, and SnS 2 @CNSs show improved sodium storage performance in terms of high specific capacity, good cycling stability, and superior rate capability.

Nanospace confined N,P co-doped carbon foams as anode for highly reversible and high capacity sodium ions batteries

Non-graphitic carbons have shown great potential in sodium ions batteries, however, major hurdle to address is the poor capacity performance. Herein, a facile strategy combining supramolecular chemistry polymerization and nanospace confinement carbonization is proposed to construct interconnected carbon foams with N,P co-doping (MNNPCs) to improve sodium storage performance. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that defined MNNPCs display fast charge transfer at the electrode-electrolyte interface. And the Na+ diffusion coefficient in the MNNPCs electrodes (1.2 × 10−10 cm2 s−1) is about 22 times than that of reference electrode, suggesting excellent sodium ions diffusion kinetics in MNNPCs electrodes. In particular, MNNPCs are capable of delivering superior specific capacity of 394.5 mAh g−1 at 50 mA g−1 after 100 cycles with an initial coulombic efficiency of 58.7%. Such architecture provides a promising structural platform for the preparation of carbon anode materials for high reversible and high capacity sodium ions batteries.