Ion Storage Performance Research Articles

Understanding the origin of the improved sodium ion storage performance of the transition metal oxide@carbon nanocomposite anodes.

Transition metal oxide (TMO) anodes show inferior sodium ion storage performance compared with that of lithium ion storage owing to the larger radium size and heavier elemental mass of Na+ than Li+. Effective strategies are highly desired to improve the Na+ storage performance of TMOs for applications. In this work, using ZnFe2O4@xC nanocomposites as model materials for investigation, we found that by manipulating the particle sizes of the inner TMOs core and the features of outer carbon coating, the Na+ storage performance can be significantly improved. The ZnFe2O4@1C with a diameter of the inner ZnFe2O4 core of around 200nm coated by a thin carbon layer of around 3nm shows a specific capacity of only 120 mA h g-1. The ZnFe2O4@6.5C with a diameter of the inner ZnFe2O4 core of around 110nm embedding in a porous interconnected carbon matrix displays a significantly improved specific capacity of 420 mA h g-1 at the same specific current. Furthermore, the latter shows an excellent cycling stability of 1000 cycles with a capacity retention of 90% of the initial 220 mA h g-1 specific capacity at 1.0Ag-1. TEM, electrochemical impedance spectroscopy, and kinetic analysis show that the inner ZnFe2O4 core with reduced particle size and the outer thicker and interconnected carbon matrix synergistically improve the active reaction sites, integrity, electric conductivity, and pseudocapacitive-controlled contribution of ZnFe2O4@xC nanocomposites, thus leading to an overall enhanced Na+ storage performance. Our findings create a universal, facile, and effective method to enhance the Na+ storage performance of the TMO@C nanomaterials.

Yolk-shell V2O3/nitrogen-doped carbon spheres as an ultra-long life anode for half/full sodium-ion batteries

With abundant resources and multiple electron transfer, V2O3 is a potential anode material for sodium ion batteries (SIBs). However, dramatic volume changes and slow reaction kinetics during the charge/discharge process still limit its application. Herein, porous yolk-shell V2O3/nitrogen-doped carbon (V2O3/NC) spheres are produced by a simple solvothermal method combined with subsequent carbonization. In this hierarchical structure, ultra-fine nanoparticles as primary building unit facilitate ion/electron transport; unique yolk-shell structure relieves the volume strain improving the structure integrity; nitrogen-doped carbon enhances electrochemical conductivity; moreover, rational mesoporous structure accelerates electrolyte penetration and high specific surface area supplies abundant reaction sites. Based on the above merits, yolk-shell V2O3/NC spheres exhibit satisfactory sodium ion storage performance (129.5 mAh g−1 at 5.0 A g−1 after 12,000 ultra-long cycles). What's more, an assembled V2O3/NC//Na3V2(PO4)3 full cell displays outstanding cycle performance (46 mAh g−1 after 300 cycles at 0.2 A g−1), demonstrating its potential value for practical applications.

Facile synthesis of Mn2O3/Mn3O4 composites with superior zinc ion storage performance

Mn2O3/Mn3O4 composites are synthesized by a facile thermal decomposition strategy with MnCl2·4H2O and sucrose as raw materials. The addition of sucrose induces the phase structure of manganese oxides to transform from single Mn2O3 into Mn2O3/Mn3O4 composites, reduction of particle size, and much-enhanced zinc storage performances. The Mn2O3/Mn3O4 sample (MO-1.0) prepared with the Mn2+/sucrose molar ratio of 1:1 exhibits the best zinc storage performances, delivering a high specific capacity of 345 mA h g−1 at 200 mA g−1 after 120 discharge/charge cycles and 122 mA h g−1 at 1000 mA g−1 after 1000 discharge/charge cycles. At the current density of 2000 mA g−1, it also delivers a high specific capacity of 143.3 mA h g−1. The present work offers a facile and cost-efficient method for preparing high-performance Mn2O3/Mn3O4 composite cathode materials of ZIBs.

Enhanced zinc ion storage performance of V2O5·nH2O prepared by hydrothermal method with the assistance of sodium dodecylbenzene sulfonate

V2O5·nH2O is an attractive cathode material for aqueous zinc ion batteries (ZIBs) due to its high theoretical capacity, layered structure, and large interlayer distance. However, it suffers sluggish Zn2+ diffusivity, poor rate capability, and the collapse of lamellar structure during cycling, which severely limits its practical application. In this work, a NaxV2O5·nH2O (VO-SDBS) sample is synthesized by a facile hydrothermal method with the assistance of sodium dodecyl benzene sulfonate (SDBS). The microstructure of the samples is characterized by XRD, SEM, and XPS. The electrochemical property of the samples is examined by CV, EIS, charge-discharge test, and galvanostatic intermittent titration technique (GITT) measurement. The SDBS plays the role of Na+ source and structure directing agent. Due to the 3D interweaved nanofiber-like morphology and the stabilizing effect of pre-intercalated Na+, the as-prepared VO-SDBS sample exhibits an outstanding rate capability (maintaining a specific capacity of 88 mA h g−1 even at an ultra-high current density of 20.0 A g−1), superior cyclability (with a reversible capacity of 223 mA h g−1 after 3000 cycles at 5.0 A g−1), and enhanced Zn2+ diffusivity. This work provides a simple and effective strategy to enhance the zinc ion storage properties of V2O5·nH2O from the aspects of morphology control and metal cation pre-intercalation.

Synergistic effect on the improved lithium ion storage performance in the porous Fe2O3@Fe3C@C composite

The porous Fe2O3@Fe3C@C composite was synthesized by a simple two-step thermal treatment and its structure, morphology, lithium ion storage performance and diffusion kinetics were discussed. Benefitting from the high theoretical capacity of Fe2O3 and fast kinetics of Fe3C, the Fe2O3@Fe3C@C composite exhibits a stable cycling capacity of 800.3 mAh g−1 after 100 cycles at 0.1 A g−1 with superior rate capability. The CV and in-situ EIS analysis results reveal that the Fe2O3@Fe3C@C composite has reversible redox reaction, stable solid electrolyte interphase films and low charge transfer resistance during the discharging and charging process. In addition, the lithium ion diffusion coefficients of the Fe2O3@Fe3C@C composite at different voltage states are investigated by GITT measurement. This work can provide an effective strategy for synthesis of metal oxide@metal carbide composite for lithium-ion batteries.

Unleash sodium storage potential of MoS2 nanosheets: Generating favorable kinetics from optimal crystallinity and elaborate structure

Metal oxides with high crystallinities have been reported to exhibit better ion storage performances, which demonstrates the significance of controlling the crystallinity as a facile and economical method to synthesize high-performance electrode materials. However, the relationship between crystallinity and charge storage property remains unclear for transition metal disulfides (TMDs). In this work, we employ a series of MoS2-based electrode materials with different crystallinities as a case to study the trend in sodium ion (Na+) storage characteristics of TMDs with varying crystallinity. Structure characterizations prove that the crystallinity of MoS2 improves with the increase in calcination temperature. Electrochemical tests and kinetic analyses indicate that MoS2-based electrode material with higher crystallinity shows better high-rate Na+ storage performance and stronger pseudocapacitive response. Finally, we carry out density functional theory calculations to study Na+ diffusion behaviors in MoS2 with different crystallinities, and we prove that MoS2 with higher crystallinity possesses better Na+ diffusion kinetics. The conclusions of this work provide beneficial guidance for the rational design of TMDs toward superior high-rate ion storage.

Synthesis and lithium ion storage performance of novel two dimensional vanadium niobium carbide (VNbCTx) MXene

Two-dimensional double transition metal carbides/nitride with unique out-of-plane arrangement of two metal atoms is emerging as a new pseudocapacitor material and attracting wide attention in the field of energy storage. Herein, fabrication of a novel 211-phase vanadium niobium carbide (VNbCTx) MXene by selectively etching the Al atomic layer from its VNbAlC MAX phase is reported for the first time. Effect of etching parameters on the microstructure, crystallinity, and electrochemical property of multilayer VNbCTx is examined. As the electrode material of lithium ion batteries, VNbCTx show a higher specific capacity of 520.5 mAh g−1 at 0.1 A g−1 and promising cycle stability. This work provides additional understanding about the synthesis and storage performance of double transition metal MXene, which will benefit the development of novel double transition metal MXene for energy storage applications.

Rational construction of metal-organic framework derived dual-phase doping N-TiO2 plus S-carbon yolk-shell nanodisks for high-performance lithium ion batteries

Known as a low-strain anode material for lithium ion batteries (LIBs), the poor electronic/ionic conductivity of TiO2 is threatening to achieve satisfactory lithium ion storage performance. Herein, dual-phase doping combined with structure design strategy is carried out to construct yolk-shell nanodisks decorated with N-doped TiO2 nanosheets, S-doped carbon and conductive Ni nanoparticles (N-TiO2/S-C/Ni) to realize enhanced electrochemical performance. Thanks to the N-doping in TiO2 and S-doping in metal organic frameworks (MOFs) derived carbon, the lithium ion adsorption energy of the composite can be enhanced to promote kinetic process, which is proved by density functional theory (DFT). Moreover, the elaborate yolk-shell structure with great specific surface area and abundant holes will induce plentiful sites for electrochemical reaction and make the transport pathway of ions/electrons shorter. Profiting from the above appealing features, the N-TiO2/S-C/Ni electrode displays a high capacity of 649 mAh g−1 at 0.1 A g−1 and 441 mAh g−1 at 1 A g−1 after cycling with the Coulombic efficiency of nearly 100%. On top of that, TiO2//LiFePO4 full batteries are assembled to estimate the practical value of N-TiO2/S-C/Ni.

Improved lithium ion storage performance of Ti3C2Tx MXene@S composite with carboxymethyl cellulose binder

MXenes are regarded as promising electrode materials for lithium-ion batteries owing to their high electrical conductivity and two-dimensional structure but suffer from low intrinsic specific capacities. In this study, we fabricate sulphur-doped multilayer Ti3C2Tx MXenes via calcination and annealing using sublimed sulphur as the sulphur source. After sulphur doping, the interlayer spacing of Ti3C2Tx increases, which is favourable for Li-ion insertion. The Ti3C2Tx MXene@S composite exhibits excellent electrochemical performance. A high reversible specific capacity of 393.8 mAh g−1 at a current density of 100 mA g−1 after 100 cycles is obtained. Additionally, a negative fading phenomenon is observed when the specific capacity increases to 858.9 mAh g−1 after 2550 cycles at 1 A g−1 and to 322.2 mA h g−1 after 3600 cycles at 5 A g−1 from the initial 267.3 mAh g−1. We systematically investigate the effects of two different binders (polyvinylidene difluoride and carboxymethyl cellulose, hereinafter abbreviated as PVDF and CMC, respectively) on the electrochemical performance of the Ti3C2Tx MXene@S composite and discovered that the electrode using the CMC binder exhibits better lithium-ion storage performance than that using the PVDF binder, which is attributed to the lower charge transfer resistance, higher ion diffusivity, and enhanced adhesion force.

Improved ions storage performance for various batteries: Anatase TiO2 with high-concentration of Ti vacancies

Anatase TiO2 is a promising anode material due to its high stability during the electrochemical process. Nevertheless, the slow diffusion coefficient of the metallic ions and insufficient storage sites seriously prevent its further applications in “beyond Li-ion” batteries (such as Na- and Mg-ion batteries). Herein, we prepare the anatase TiO2 with high-concentration Ti vacancies (TiO2–V) electrode through a simple solvothermal and subsequent calcination process. The XRD Rietveld, Electron Paramagnetic Resonance (EPR), Hall effect, Nuclear Magic Resonance (NMR) and X-ray Photoelectron Spectroscopy (XPS) are carried out to characterize the Ti vacancies. The TiO2–V delivers better battery performance than the stoichiometric anatase (TiO2–S) for storing various metallic ions (Li+/Na+/Mg2+). The Ti vacancies can act as additional ion storage sites and provide more open channels for metal ions transfer. This work systematically investigates the effect of Ti cation vacancies on the performance of metal-ion batteries and expands the application of cation vacancies.

Exploring the effect of different additives on the preparation of α-Mn2O3/Mn3O4 composites and their zinc ion storage performances

Exploring the effect of different additives on the preparation of α-Mn2O3/Mn3O4 composites and their zinc ion storage performances

Three‐dimensional Honeycomb MoP@C Nanocomposite with Advanced Sodium/Potassium Ion Storage Performance

AbstractMoP@C nanocomposite, combined three‐dimensional (3D) honeycomb carbon matrix with molybdenum phosphide, was synthesized through a simple hard template method followed by high‐temperature phosphating treatment. The MoP@C has shown excellent sodium and potassium‐ion storage properties applied as anode materials for sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs). The MoP@C composite maintains a high reversible specific capacity of 250 mAh g−1 in SIBs after 100 cycles at 0.5 A g−1. Furthermore, even at a high current density of 5 A g−1, it still delivers a specific capacity of 200.5 mAh g−1. Additionally, the nanocomposite holds 147.2 mAh g−1 at a high current density of 1 A g−1 in PIBs. The excellent electrochemical performance benefits from the synergistic effect of the hierarchical MoP@C nanostructure. The exquisite porous nano‐frame with higher conductivity and larger specific surface area, the active substance is fully infiltrated in the electrolyte, and successfully shortens the diffusion distance of electrons and ions. Moreover, the cavity in the heterostructure effectively inhibits the instinctive aggregation of MoP and simultaneously alleviates the volume expansion during the intercalation and deintercalation of ions in the charge and discharge process, enabling the excellent rate performance and long cycle life of the MoP@C electrode. The designed MoP@C composite shows excellent electrochemical cycle performance and rate performance as anode materials for sodium/potassium‐ion batteries. The MoP@C composite maintained a high reversible specific capacity of 250 mAh g−1 in sodium‐ion batteries after 100 cycles at the current density of 0.5 A g−1. Furthermore, even at a high current density of 5 A g−1, it still delivered a specific capacity of 200.5 mAh g−1. Moreover, MoP@C composite materials also show excellent performance as anode material of potassium‐ion batteries, with a specific capacity of 147.2 mAh g−1 at the high current density of 1 A g−1. In summary, the excellent electrochemical performance of MoP@C composite materials fully proves that they can greatly improve the stability of the structure and reversibility as electrode materials, and lays a foundation for the further application of electrochemical energy storage devices in large‐scale applications.

Designing interstitial boron‐doped tunnel‐type vanadium dioxide cathode for enhancing zinc ion storage capability

AbstractChemical doping is a powerful method to intrinsically tailor the electrochemical properties of electrode materials. Here, an interstitial boron‐doped tunnel‐type VO2(B) is constructed via a facile hydrothermal method. Various analysis techniques demonstrate that boron resides in the interstitial site of VO2(B) and such interstitial doping can boost the zinc storage kinetics and structural stability of VO2(B) cathode during cycling. Interestingly, we found that the boron doping level has a saturation limit peculiarity as proved by the quantitative analysis. Notably, the 2 at.% boron‐doped VO2(B) shows enhanced zinc ion storage performance with a high storage capacity of 281.7 mAh g−1 at 0.1 A g−1, excellent rate performance of 142.2 mAh g−1 at 20 A g−1, and long cycle stability up to 1000 cycles with the capacity retention of 133.3 mAh g−1 at 5 A g−1. Additionally, the successful preparation of the boron‐doped tunnel‐type α‐MnO2 further indicates that the interstitial boron doping approach is a general strategy, which supplies a new chance to design other types of functional electrode materials for multivalence batteries.

Hollandite-type VO1.52(OH)0.77 nanorod arrays on carbon cloth toward the improvement of zinc diffusion

As cathodes for aqueous zinc ion batteries (ZIBs), vanadium-based materials have received a lot of attention in recent years because of their high theoretical capacities and suitable working potentials. However, the sluggish kinetics and volume expansion effects lead to their rapid capacity decay and poor rate performance. Herein, a novel strategy is proposed through the in-situ growth of one-dimensional hollandite-type VO1.52(OH)0.77 nanorod arrays on flexible carbon fiber cloth as ZIBs cathode material. The synergistic effect between the hollandite-type tunnel structure and the functional group-modified conductive collector, not only accelerates the charge transfer rate and increases zinc ion intercalation capacity but also enhances the structural stability of the electrode by improving the interface stability and alleviating the detachment between the VO1.52(OH)0.77 nanorod arrays and the conducting substrate during the charge/discharge process. Benefitting from these merits, as-prepared VO1.52(OH)0.77 achieves an impressive reversible capacity of 305.6 mAh g−1 at 100 mA g−1 and ultralong cyclic stability (96.4% retention over 1000 cycles). This work reveals a concise approach to the construction of hollandite-type and demonstrates that the structural stability of vanadium-based oxide cathodes can be significantly enhanced by elegant structural design, thereby improving their Zn ion storage performance.

Nitrogen doped porous carbon with high rate performance for lithium ion storage

Amorphous carbon has been studied in anode electrode materials of lithium ion batteries (LIBs) due to its rich resources and adjustable structure. However, due to its low conductivity, it shows poor rate performance. In this work, amorphous nitrogen doped porous carbon (NDPC) was synthesized by salt template method using ionic liquid (C10H15N5) as sources of carbon and nitrogen. The structure characterization shows that there is an interaction between the introduction of nitrogen atoms and porous structure: nitrogen doping can promote charge transfer, and porous carbon structure can reduce the diffusion path of lithium ions. Therefore, the NDPC shows excellent lithium ion diffusion ability and good electronic conductivity. When NDPC is applied to the anode material of LIBs, it shows a superior lithium ion storage performance of 412 mA h g−1 after 200 cycles at a current density of 1860 mA g−1. The study provides favorable conditions for the development of carbon anode materials with in situ heteroatom doping and porous structure.

Three-dimensional heterogeneity in liquid electrolyte structures promotes Na ion transport and storage performance in Na-ion batteries.

Unlike solid materials, the molecular structure and chemical distribution in electrolyte solutions have been considered in isotropic states. Herein, we reveal controllable regulation of solution structures in electrolytes by manipulating solvent interactions for Na-ion batteries. Low-solvation fluorocarbons as diluents in concentrated phosphate electrolytes induce adjustable heterogeneity in electrolyte structures through variable intermolecular forces between high-solvation phosphate and diluents. An optimal trifluorotoluene (PhCF3) diluent weakens the solvation strength around Na+ and spontaneously leads to a locally enlarged Na+ concentration and global 3D continuous Na+ transport path thanks to the appropriate electrolyte heterogeneity. Besides, strong correlations between the solvation structure and the Na+ storage performance and interphases are demonstrated. PhCF3 diluted concentrated electrolyte enables superior operations of Na-ion batteries at both room temperature and a high temperature of 60 °C. A hard carbon anode exhibits a reversible capacity of 300 mA h g-1 at 0.2C and excellent life over 1200 cycles without decay.

Carbon confined GeO2 hollow spheres for stable rechargeable Na ion batteries.

Germanium (Ge) based nanomaterials are regarded as promising high-capacity anode materials for Na ion batteries, but suffer fast capacity fading problems caused by the alloying/de-alloying reactions of Na-Ge. Herein, we report a new method for preparing highly dispersed GeO2 by using molecular-level ionic liquids (ILs) as carbon sources. In the obtained GeO2@C composite material, GeO2 exhibits hollow spherical morphology and is uniformly distributed in the carbon matrix. The as-prepared GeO2@C exhibits improved Na ion storage performances including high reversible capacity (577 mA h g-1 at 0.1C), rate property (270 mA h g-1 at 3C), and high capacity retention (82.3% after 500 cycles). The improved electrochemical performance could be attributed to the unique nanostructure of GeO2@C, the synergistic effect between GeO2 hollow spheres and the carbon matrix ensures the anode material effectively alleviates the volume expansion and the particle agglomeration problems.

Construction of diphenic acid molecular welded Ti3C2 with enlarged and stable interlayer spacing towards high rate alkali metal ions storage

Ti3C2-MXene has been generally studied in energy storage area because of adjustable surface chemistry, excellent electronic conductivity, and unique layered structure. However, the diffusion kinetic performance of alkali metal ions in Ti3C2 is restricted by the limited interlayer spacing. Enlarging interlayer spacing of Ti3C2 is beneficial to improve the ion diffusion rate. Here, a simple and effective diphenic acid (DHA) molecular welding strategy is reported to prepare DHA welded Ti3C2 (DHA-Ti3C2) by dehydration condensation reaction. The welded DHA molecule contributes the dual effects of pillar and strain on the layered structure of Ti3C2, which can improve ion diffusion kinetic performance and alleviate volume expansion during the alkali metal ions insertion/extraction process. The DHA-Ti3C2 exhibits high rate capability and long-term cycle stability because of the enlarged interlayer spacing and enhanced structure stability. The specific capacity of 444 mAh g−1 and 156 mAh g−1 at current density of 0.1 A g−1 can be reached after 200 cycles and 1700 cycles in Li+/Na+ batteries, respectively. This study offers a strategy to efficiently tuning the layered structure of two-dimensional (2D) materials for achieving the optimal alkali metal ions storage performance.

Colloidal silicon dioxide assisted ethylene glycol combustion synthesis of mesoporous zinc manganate for lithium ions storage

Mesoporous zinc manganate (ZnMn2O4) hollow architectures made up of interlinked nanoparticles have been successfully prepared through a colloidal silicon dioxide (SiO2)-assisted ethylene glycol (EG) combustion process. The dosage of colloidal SiO2 plays a vital role in the morphology and specific surface area (SSA). The SSA of ZnMn2O4-EG-400 can achieve 163.2 m2 g−1 with the pore sizes mainly centered at 3.5, and 5.1 nm when the volume of colloidal silica is 400 μL. The hierarchical mesoporous feature of ZnMn2O4 hollow architectures makes it a potential electroactive material for lithium-ion storage. When mesoporous ZnMn2O4-EG-400 is employed in lithium-ion batteries, the mesoporous zinc manganate appears large specific capacity, remarkable rate performance, and durability. A reversible capacity of 384.4 mAh g–1 can be gained after 500 continuous galvanostatic charge/discharge (GCD) cycles at 1 A g–1. The outstanding lithium ions storage performance can be attributed to the high SSA and hierarchical mesoporous traits, which can afford abundant active sites, raise the contact area between Li+ and ZnMn2O4, and buffer volume change during consecutive electrochemical processes.

Regulation of low-spin Fe of Mn-iron hexacyanoferrate for boosted potassium ion storage performance

K2Fe[Fe(CN)6] (KFHCF) is promising cathode material for potassium-ion batteries (PIBs). However, it suffers from limited capacity, poor cycling, and rate capability during cycling. Here, the low-spin Fe species coordinated with carbon atoms from cyanogen ligands (FeLS-C) are regulated and activated by manganese (Mn) substitution. The regulation is systematically investigated through theoretical simulation and experiments. The original electron configuration (t2g6eg0) of FeLS-C is changed with appropriate Mn-substitution (t2g3eg2), which improves the utilization of FeLS-C, accelerates the redox charge transfer and enhances the electrical conductivity of the material. The resultant K2Mn0.1Fe0.9[Fe(CN)6] (KMFHCF-0.1) delivers an improved reversible capacity of 135 mAh·g−1 at 100 mA g−1 while the capacity of pure KFHCF is only 118 mAh·g−1. It also demonstrates excellent rate performance (76 mAh·g−1 at 800 mA·g−1) and long cycling stability (0.3% capacity degradation per cycle over 200 cycles). Ex-situ measurements verify that the cathode undergoes a highly reversible solid solution process during K-ions insertion/extraction. The full cells with hard carbon anodes demonstrate a high reversible capacity of 110 mAh·g−1 and considerable energy density of 275 Wh·kg−1 as well as excellent cyclability and favorable rate performance. This work expands the design pathways for Prussian blue analogs cathode materials.