Rate Capability For Sodium-ion Batteries Research Articles

Delving into the dissimilarities in electrochemical performance and underlying mechanisms for sodium and potassium ion storage in N-doped carbon-encapsulated metallic Cu2Se nanocubes

The large volumetric variations experienced by metal selenides within conversion reaction result in inferior rate capability and cycling stability, ultimately hindering the achievement of superior electrochemical performance. Herein, metallic Cu2Se encapsulated with N-doped carbon (Cu2Se@NC) was prepared using Cu2O nanocubes as templates through a combination of dopamine polymerization and high-temperature selenization. The unique nanocubic structure and uniform N-doped carbon coating could shorten the ion transport distance, accelerate electron/charge diffusion, and suppress volume variation, ultimately ensuring Cu2Se@NC with excellent electrochemical performance in sodium ion batteries (SIBs) and potassium ion batteries (PIBs). The composite exhibited excellent rate performance (187.7 mA h g−1 at 50 A g−1 in SIBs and 179.4 mA h g−1 at 5 A g−1 in PIBs) and cyclic stability (246.8 mA h g−1 at 10 A g−1 in SIBs over 2500 cycles). The reaction mechanism of intercalation combined with conversion in both SIBs and PIBs was disclosed by in situ X-ray diffraction (XRD) and ex situ transmission electron microscope (TEM). In particular, the final products in PIBs of K2Se and K2Se3 species were determined after discharging, which is different from that in SIBs with the final species of Na2Se. The density functional theory calculation showed that carbon induces strong coupling and charge interactions with Cu2Se, leading to the introduction of built-in electric field on heterojunction to improve electron mobility. Significantly, the theoretical calculations discovered that the underlying cause for the relatively superior rate capability in SIBs to that in PIBs is the agile Na+ diffusion with low energy barrier and moderate adsorption energy. These findings offer theoretical support for in-depth understanding of the performance differences of Cu-based materials in different ion storage systems.

Construction of Three-Dimensional Hierarchical CoSe2 Microflowers Assembled by Thin Nanosheets for High-Performance Sodium-Ion Batteries

Transition metal selenides are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, they suffer from large volume change, serious polyselenide dissolution and sluggish reaction kinetics during charge/discharge process, resulting in poor cycling stability and low rate performance for SIBs, which further restrict their widespread application. Here, we developed carbon-free three-dimensional (3D) hierarchical microflower-shaped CoSe2 with a diameter size of approximately 2[Formula: see text][Formula: see text]m, composed of nanosheets through a one-step solvothermal method. The thin nanosheets are conducive to shortening the Na[Formula: see text] diffusion channels and relieving the volume expansion, and the 3D hierarchical microflower architecture could effectively prevent the agglomeration of nanosheets; accordingly, the resulting CoSe2 microflowers deliver a high specific capacity of 451.94[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] even at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] after 100 cycles, compared with CoSe2 nanoparticles. This work offers an approach for designing metal selenides with high capacities and rate capability for SIBs.

A distinctive strategy of Sb doped quaternary oxide cathodes materials toward energy storage of electric equipment for sodium-ion batteries

The poor cycle stability and rate capability for sodium-ion batteries is largely due to electrochemical irreversibility and sluggish mobility of Na+ in the cathode materials. Herein, a new strategy of introducing Sb ions into the ternary oxide NiMnTi-based layer-structured cathode material is designed. Reversible phase transition in this cathode NMTSb0.03 restraint the rapid capacity decay issued from intense volume variation, exhibiting a reversible capacity of 147.8 mAh g−1 and retaining 103.5 mAh g−1 over 200 cycles at 1C. The enough space after Sb substitution allows the effective accommodation of Na+ intercalation and deintercalation, affording a specific capacity of 90 mAh g−1 at 8C. The improvement is attributed to the enhanced Na+ diffusion kinetics with the meliorative equilibrium conductance and the higher cohesive energy after Sb doping. Considering its simple preparation and scale-up capability, the O3-type NaNi0.5Mn0.3Ti0.2O2 with Sb5+may find extensive applications in designing electrode for sodium-ion batteries.

Constructing a VS4–V2CTx heterojunction interface to realize an ultra-long lifetime and high rate capability in sodium-ion batteries

A superior electrochemical performance is achieved by constructing VS4–V2CTx Schottky contact heterojunctions with built-in electric fields that accelerate the kinetics of electron and Na+ diffusion.

Ball Milling Solid-State Synthesis of Highly Crystalline Prussian Blue Analogue Na2-x MnFe(CN)6 Cathodes for All-Climate Sodium-Ion Batteries.

With a series of merits, Prussian blue analogs (PBAs) have been considered as superior cathode materials for sodium-ion batteries (SIBs). Their commercialization, however, still suffers from inferior stability, considerable [Fe(CN)6 ] defects and interstitial water in the framework, which are related to the rapid crystal growth. Herein, a "water-in-salt" nanoreactor is proposed to synthesize highly crystallized PBAs with decreased defects and water, which show both superior specific capacity and rate capability in SIBs. The air-stability, all-climate, and full-cell properties of our PBA have also been evaluated, and it exhibits enhanced electrochemical performance and higher volume yield than its counterpart synthesized via the water-based co-precipitation method. Furthermore, their highly reversible sodium-ion storage behavior has been measured and identified via multiple in situ techniques. This work could pave the way for the PBA-based SIBs in grid-scale energy-storage systems.

Ball Milling Solid‐State Synthesis of Highly Crystalline Prussian Blue Analogue Na2−xMnFe(CN)6 Cathodes for All‐Climate Sodium‐Ion Batteries

AbstractWith a series of merits, Prussian blue analogs (PBAs) have been considered as superior cathode materials for sodium‐ion batteries (SIBs). Their commercialization, however, still suffers from inferior stability, considerable [Fe(CN)6] defects and interstitial water in the framework, which are related to the rapid crystal growth. Herein, a “water‐in‐salt” nanoreactor is proposed to synthesize highly crystallized PBAs with decreased defects and water, which show both superior specific capacity and rate capability in SIBs. The air‐stability, all‐climate, and full‐cell properties of our PBA have also been evaluated, and it exhibits enhanced electrochemical performance and higher volume yield than its counterpart synthesized via the water‐based co‐precipitation method. Furthermore, their highly reversible sodium‐ion storage behavior has been measured and identified via multiple in situ techniques. This work could pave the way for the PBA‐based SIBs in grid‐scale energy‐storage systems.

Fabricating multi-porous carbon anode with remarkable initial coulombic efficiency and enhanced rate capability for sodium-ion batteries

Due to the abundant sodium reserves and high safety, sodium ion batteries (SIBs) are foreseen a promising future. While, hard carbon materials are very suitable for the anode of SIBs owing to their structure and cost advantages. However, the unsatisfactory initial coulombic efficiency (ICE) is one of the crucial blemishes of hard carbon materials and the slow sodium storage kinetics also hinders their wide application. Herein, with spherical nano SiO2 as pore-forming agent, gelatin and polytetrafluoroethylene as carbon sources, a multi-porous carbon (MPC) material can be easily obtained via a co-pyrolysis method, by which carbonization and template removal can be achieved synchronously without the assistance of strong acids or strong bases. As a result, the MPC anode exhibited remarkable ICE of 83% and a high rate capability (208 mAh/g at 5 A/g) when used in sodium-ion half cells. Additionally, coupling with Na3V2(PO4)3 as the cathode to assemble full cells, the as-fabricated MPC//NVP full cell delivered a good rate capability (146 mAh/g at 5 A/g) as well, implying a good application prospect the MPC anode has

Suppressing O3−O’3 phase transition in NaCrO2 cathode enabling high rate capability for sodium-ion batteries by Sb substitution

Poor rate capability of cathode materials for sodium-ion batteries (SIBs) is one of the major obstacles hindering practical application of SIBs due to the large ion radius of Na+ and its sluggish kinetics. Improving rate capability for SIBs is a critical issue. Herein, we reveal that introducing small amount of Sb into O3-NaCrO2 can improve the rate capability of NaCrO2 cathode significantly. The occupation of Sb in Cr sites can expand the c/a ratio and the unit cell volume, thus promoting sodium diffusion in the a-b channels. Under a high rate of 5C, the 5% Sb-substituted Na0.9Cr0.95Sb0.05O2 (NCS-0.05) shows a reversible capacity of 114 mAh g−1 with capacity retention of 70.9% after 1000 cycles. Under an ultrahigh current rate of 32C, a reversible capacity of 96.1 mAh g−1 can still be maintained. Synchrotron in situ X-ray diffraction results reveals highly reversible phase transition behavior of NCS-0.05 during cycling even under high rates, and the O3 → O’3 phase transition in NaCrO2 is suppressed effectively by Sb substitution. Density functional theory calculations indicate that Sb substitution can also lower desodiation energy and decrease the bandgap of NaCrO2, leading to improved reaction kinetics and electronic conductivity.

Boosting Reversibility of Mn-Based Tunnel-Structured Cathode Materials for Sodium-Ion Batteries by Magnesium Substitution.

Electrochemical irreversibility and sluggish mobility of Na+ in the cathode materials result in poor cycle stability and rate capability for sodium‐ion batteries. Herein, a new strategy of introducing Mg ions into the hinging sites of Mn‐based tunnel‐structured cathode material is designed. Highly reversible electrochemical reaction and phase transition in this cathode are realized. The resulted Na0.44Mn0.95Mg0.05O2 with Mg2+ in the hinging Mn‐O5 square pyramidal exhibits promising cycle stability and rate capability. At a current density of 2 C, 67% of the initial discharge capacity is retained after 800 cycles (70% at 20 C), much improved than the undoped Na0.44MnO2. The improvement is attribute to the enhanced Na+ diffusion kinetics and the lowered desodiation energy after Mg doping. Highly reversible charge compensation and structure evolution are proved by synchrotron‐based X‐ray techniques. Differential charge density and atom population analysis of the average electron number of Mn indicate that Na0.44Mn0.95Mg0.05O2 is more electron‐abundant in Mn 3d orbits near the Fermi level than that in Na0.44MnO2, leading to higher redox participation of Mn ions.

Freestanding Sodium Vanadate/Carbon Nanotube Composite Cathodes with Excellent Structural Stability and High Rate Capability for Sodium-Ion Batteries.

Sodium vanadate NaV6O15 (NVO) is one of the most promising cathode materials for sodium-ion batteries because of its low cost and high theoretical capacity. Nevertheless, NVO suffers from fast capacity fading and poor rate capability. Herein, a novel free-standing NVO/multiwalled carbon nanotube (MWCNT) composite film cathode was synthesized and designed by a simple hydrothermal method followed by a dispersion technique with high safety and low cost. The kinetics analysis based on cyclic voltammetry measurements reveals that the intimate integration of the MWCNT 3D porous conductive network with the 3D pillaring tunnel structure of NVO nanorods enhances the Na+ intercalation pseudocapacitive behavior, thus leading to exceptional rate capability and long lifespan. Furthermore, the NVO/MWCNT composite exhibits excellent structural stability during the charge/discharge process. With these benefits, the composite delivers a high discharge capacity of 217.2 mA h g-1 at 0.1 A g-1 in a potential region of 1.5-4.0 V. It demonstrates a superior rate capability of 123.7 mA h g-1 at 10 A g-1. More encouragingly, it displays long lifespan; impressively, 96% of the initial capacity is retained at 5 A g-1 for over 500 cycles. Our work presents a promising strategy for developing electrode materials with a high rate capability and a long cycle life.

Tremella-like porous carbon derived from one-step electroreduction of molten carbonates with superior rate capability for sodium-ion batteries

As a promising alternative, sodium-ion batteries (SIBs) have been one of the hottest topics for emerging energy storage and conversion. Hard carbon (HC) material is kinetically favorable for sodium and electron transportation due to the amorphous structure with enlarged interlayer space. In this work, we report the electrochemical sodium storage behavior of tremella-like porous carbon synthesized via one-step electroreduction of molten Li-Na-K carbonates. As-prepared electrolytic carbon at 500 °C (C-500) and 6 V exhibits an interconnected micro-meso-macroporous structure with a high specific surface area of 691.77 m2 g−1. As an anode for SIBs, the C-500 sample exhibits high initial specific capacity of 402.1 mA h g−1 at 0.05 A g−1, superior rate performance (108 mA h g−1 after 1000 cycles at 5 A g−1) and wonderful cycling stability. The synergistic effect of unique porous structure and double surface capacitive storage characteristics lead to the exceptional performance. This work provides a facile pathway for the synthesis of novel carbon structure via molten salts electrolysis for SIBs application.

Electrochemical Properties of Chemical Composition-Tuned SnPx/C Nanocomposite Anode in a Sodium-Ion Battery

Tin phosphides (SnPx) has been considered as one of the most promising anode materials for sodium-ion batteries (SIBs) due to the high theoretical volumetric and gravimetric capacities. Nevertheless, SnPx has a low electrical conductivity and undergoes the severe pulverization resulted from a large volume change during sodiation/desodiation process, which leads to rapid decline in the performance. These problems can be solved by tuning nanostructure of the composite materials composed of SnPx and conductive carbon materials. On the other hand, SnPx has three different forms depending on phosphorus (P) content, Sn4P3, SnP, and SnP3, the higher the P content provide the higher theoretical capacity because the theoretical capacity of P is about three times higher than metallic tin. However, only a method using ball milling has been reported for the synthesis of SnPx having a high P content, and the nanostructure can’t be precisely controlled by this method [1]. Additionally, solvothermal method between metallic tin and red P allows to prepare thenanostructured SnPx/C composite, however, it gives only Sn4P3 phase which has the lowest P content [2]. In this work, to suggest the appropriate nanostructure and P content to obtain the high reversible capacity of SnPx as well as improved rate capability in SIBs, we synthesized hybrid nanocomposites composed of size-controlled SnPx (x = 3/4, 1, and 3) nanoparticles and low-dimensional carbon material by a facile direct reaction method between liquid phase tin and gas phase P. Through this method, we could control the Sn/P composition by regulating of cooling rate after reaction and P partial pressure in a reactor, which is confirmed by XRD analysis of Fig. 1(a). Using the three types of as-prepared SnPx/C composites with different P contents and nanostructures., we investigated their electrochemical properties for sodium ion battery anodes The obtained SnPx/C nanocomposite with x=3/4, 1, and 2 showed 500, 610, and 810 mAh g-1 of reversible capacities, respectively, as anode active materials of SIBs. Although SnPx with the higher the P content gave the enhanced reversible capacity, the poor rate capability and cycle durability were obtained presumably due to the increased internal resistance components and volume expansion ratio. For this reason, SnPx/C anode requires the empty space, where the volume expansion of sodiated SnPx can be accommodated without pulverization. Specifically, by preparing the Yolk-shell structured SnP/C (Y-SnP/C) composite (Fig. 1(b)), we achieved 3 times larger capacity retention at 3.2 A g-1 of current density as shown in Fig. 1(c).

Nano-NaVPO4F enwrapped in reduced graphene oxide as a cathode material for long-cycle and high-rate sodium-ion batteries

Nano-NaVPO4F enwrapped in reduced graphene oxide is obtained via the modified freeze-drying method. In the composite, reduced graphene oxide constitutes a 3D conductive framework, and NaVPO4F particles less than 100 nm are uniformly enwrapped in the graphene sheets. The composite exhibits not only excellent cycle stability but also extraordinary rate capability in sodium-ion batteries. The corresponding discharge capacities at 10, 20, 50, and 100 C are 113.9, 112.1, 106.9, and 86.6 mAh g−1, respectively. In particularly, it delivers an initial discharge specific capacity of 110.6 mAh g−1 while obtains 100.0 mAh g−1 with the capacity retention of 90.4% at 10 C after 3000 cycles. Such superior performance can be ascribed to the uniform nanometer-sized particles and the 3D conductive graphene framework. This work implies that graphene-modified NaVPO4F can be a promising cathode material for long-cycle and high-rate sodium-ion batteries.

Lath-shaped biomass derived hard carbon as anode materials with super rate capability for sodium-ion batteries

Biomass wastes or biomass derived hard carbon materials with the advantages of green, as well as economic and high reversible capacity have became the promising anode materials for sodium ion batteries (SIBs). Despite this, the poor rate capability hinders their further development. Here, we synthesized lath-shaped hard carbon materials derived from peanut shells by a two-step approach, namely a hydrothermal pretreatment for different treatment time first, and then a carbonized process at 800°C. Morphology and structural characterizations (SEM, XRD and Raman) prove the hydrothermal pretreatment has a great influence on morphology transformation, the layer spacing, as well as the defect concentration which can enhance the adsorption sites of Na+ and shorten the transport route of sodium ions. The PSDHCs-4 (hydrothermal treatment for 4h) electrode can deliver the highest reversible capacity of 256±5 mAh g−1, and show the best capacity retention of 97±2% at the current rate of 0.1 C after 100cycles. More importantly, PSDHCs-4 electrode shows the excellent rate performances with a reversible capacity of 261, 244, 206, 163, 125, and 100 mAh g−1 at the current rates of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 C, respectively. These remarkable electrochemical properties indicate that PSDHCs-4 material should be a promising anode material for SIBs.

CoS@sulfur doped onion-like carbon nanocapsules with excellent cycling stability and rate capability for sodium-ion batteries

The mineral reserves of lithium severely restrict the future development and application of lithium ion batteries. Because of rich sodium reserves and the similar chemical properties between sodium and lithium, sodium-ion batteries are the promising substitute for lithium ion batteries. Sulfur doped onion-like carbon coated CoS (CoS@S-doped OLC) nanocapsules have been synthesized by the arc-discharge approach under the atmosphere of Ar, H2S and C2H5OH. The electrochemical measurements imply that the CoS@S-doped OLC nanocapsules have the potential for a superior anode materials for the rechargeable sodium ion batteries. The discharge capacity of 582 mA h g−1 can be reached over 500 cycles with the current density of 0.1 A g−1 and the averaged discharge capacities of 326 and 258 mA h g−1 are remained at 8.0 and 10.0 A g−1 for each ten cycles, respectively. The CoS@S-doped OLC nanocapsules after 500 cycles still exhibit the complete spherical shape and the doping of S in OLC shell is conductive for conductivity, ensuring the high Na+ storage performance and excellent long-term cyclability and good rate capability of CoS@S-doped OLC nanocapsules.

SnS2 /Sb2 S3 Heterostructures Anchored on Reduced Graphene Oxide Nanosheets with Superior Rate Capability for Sodium-Ion Batteries.

Tin disulfide, as a promising high-capacity anode material for sodium-ion batteries, exhibits high theoretical capacity but poor practical electrochemical properties due to its low electrical conductivity. Constructing heterostructures has been considered to be an effective approach to enhance charge transfer and ion-diffusion kinetics. In this work, composites of SnS2 /Sb2 S3 heterostructures with reduced graphene oxide nanosheets were synthesized by a facile one-pot hydrothermal method. When applied as anode material in sodium-ion batteries, the composite showed a high reversible capacity of 642 mA h g-1 at a current density of 0.2 A g-1 and good cyclic stability without capacity loss in 100 cycles. In particular, SnS2 /Sb2 S3 heterostructures exhibited outstanding rate performance with capacities of 593 and 567 mA h g-1 at high current densities of 2 and 4 A g-1 , respectively, which could be ascribed to the dramatically improved Na+ diffusion kinetics and electrical conductivity.

Cobalt Sulfide Quantum Dot Embedded N/S-Doped Carbon Nanosheets with Superior Reversibility and Rate Capability for Sodium-Ion Batteries.

Metal sulfides are promising anode materials for sodium-ion batteries due to their large specific capacities. The practical applications of metal sulfides in sodium-ion batteries, however, are still limited due to their large volume expansion, poor cycling stability, and sluggish electrode kinetics. In this work, a two-dimensional heterostructure of CoSx (CoS and Co9S8) quantum dots embedded N/S-doped carbon nanosheets (CoSx@NSC) is prepared by a sol-gel method. The CoSx quantum dots are in situ formed within ultrafine carbon nanosheets without further sulfidation, thus resulting in ultrafine CoSx particle size and embedded heterostructure. Meanwhile, enriched N and S codoping in the carbon nanosheets greatly enhances the electrical conductivity for the conductive matrix and creates more active sites for sodium storage. As a result, the hybrid CoSx@NSC electrode shows excellent rate capability (600 mAh g-1 at 0.2 A g-1 and 500 mAh g-1 at 10 A g-1) and outstanding cycling stability (87% capacity retention after 200 cycles at 1 A g-1), making it promising as an anode material for high-performance sodium-ion batteries. A CoSx@NSC//Na0.44MnO2 full cell is demonstrated, and it can deliver a specific capacity of 414 mAh g-1 (based on the mass of CoSx@NSC) at a current density of 0.2 A g-1.

Graphene-wrapped Porous Sb Anodes for Sodium-Ion Batteries by Mechanochemical Compositing and Metallomechanical Reduction of Sb2O3

Antimony metal nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were fabricated from their oxide form (Sb2O3) in a micrometer dimension using a novel two-step ball-milling process. The first mechanochemical process was designed to decrease the particle size of Sb2O3 microparticles for ensuring advantages of nano size and to subsequently coat the Sb2O3 nanoparticles with a-few-layer graphene (Sb2O3@Gn). The second metallomechanical ball-milling process reduced the oxide to its metal form (Sb@Gn) by the help of Zn as a metallic reductant. The graphene layer (@Gn) blocked the alloying reaction between Sb and Zn, limiting the size of Sb particles during the metallomechanical reduction step. During reduction, oxygen species were transferred from of Sb2O3 through @Gn to Zn along redox transfer pathways rather than direct mass transfer via unsaturated vacancies in the @Gn. the redox transfer involving oxidation of @Gn by O2− is plausible routes for O2− transfer in the metallomechanical reduction. The Sb@Gn anode exhibited outstanding capacity retention along charge/discharge cycles and improved rate capability in sodium-ion batteries. The @Gn provided conductive pathways to the Sb core and limited size expansion during sodium-lithium alloying.

FeSe2 clusters with excellent cyclability and rate capability for sodium-ion batteries

Sodium-ion batteries (SIBs) have great promise for sustainable and economical energy-storage applications. Nevertheless, it is a major challenge to develop anode materials with high capacity, high rate capability, and excellent cycling stability for them. In this study, FeSe2 clusters consisting of nanorods were synthesized by a facile hydrothermal method, and their sodium-storage properties were investigated with different electrolytes. The FeSe2 clusters delivered high electrochemical performance with an ether-based electrolyte in a voltage range of 0.5–2.9 V. A high discharge capacity of 515 mAh·g–1 was obtained after 400 cycles at 1 A·g–1, with a high initial columbic efficiency of 97.4%. Even at an ultrahigh rate of 35 A·g–1, a specific capacity of 128 mAh·g–1 was achieved. Using calculations, we revealed that the pseudocapacitance significantly contributed to the sodium-ion storage, especially at high current rates, leading to a high rate capability. The high comprehensive performance of the FeSe2 clusters makes them a promising anode material for SIBs.

Amorphous iron phosphate/carbonized polyaniline nanorods composite as cathode material in sodium-ion batteries

As-prepared polyaniline (PANI) nanorods have been used to synthesize an iron phosphate/polyaniline (FePO4/PANI) composition through the microemulsion technique. After sintering at 460 °C under a nitrogen protective atmosphere, the PANI carbonized, yielding the amorphous iron phosphate/carbonized polyaniline nanorods (FePO4/CPNRs) composite, which acts as the cathode material in sodium-ion batteries (SIBs). The electrochemical performance of FePO4/CPNRs composite shows an initial discharge specific capacity of 140.2 mAh g−1, with the discharge specific capacity being maintained at 134.4 mAh g−1 after the 120th cycle, up to 87.9 % of the theoretical capacity (154.1 mAh g−1 for NaFePO4), as well as an excellent rate capability in sodium-ion batteries. Compared with pure FePO4, the electrochemical performance has been greatly improved. On the one hand, using the CPNRs as conductive medium significantly improves electronic transport. On the other hand, the FePO4 sphere of nanoscale particles, which has a large specific surface area, can promote an active material/electrolyte interface reaction and improve the speed of sodiation and desodiation during the charge and discharge process. The amorphous FePO4/CPNRs composite shows outstanding electrochemical performance as competitive cathode material in SIBs.