Enhanced Rate Capability Research Articles

ZIF-67/Super P modified separator as an efficient polysulfide barrier for high-performance lithium‐sulfur batteries

Lithium‐sulfur battery has been regarded to be one of the most promising electrochemical energy storage devices on account of its high theoretical specific capacity, low cost and non-toxicity. Nevertheless, the practical application is largely hindered by the fast capacity attenuation, which primarily resulted from the shuttle effect of the soluble polysulfides. Herein, a ZIF 67-based separator with ion selective permeation is designed to mitigate the shuttling problem. The ZIF-67/Super P composite hinders the migration of polysulfides, while the high conductive Super P leads to efficient utilization of the trapped polysulfides in the subsequent cycles. The battery based on ZIF-67/Super P-coated separator shows a good initial specific capacity of 1341 mAh g‐1 at 0.2 C with great capacity retention and delivers enhanced rate capability. This work verifies the potential of employing MOF-based composites as the modification materials of separators for high performance lithium‑sulfur batteries.

Employing ZIF-67 architectures into 1D binder-free Co3O4-based carbon fiber composites for advanced sodium-ion storage application

Metal-organic frameworks (MOFs) have drawn numerous attention as precursors to fabricate porous materials owing to their inherent highly controllable composition and tunable porosities. Nevertheless, the construction of an efficient and low cost anode material derived from zeolitic imidazole framework-67 (ZIF-67) to pursue enhance rate capability and specific capacity remains attractive and challenging. Herein, the fabrication of the Co3O4-based hierarchical carbon fiber composites with the ZIF-67/Co2+ ions derivatives embedded (Co3O4@CNF) by a facile electrospinning technique and a two-step annealing is reported. When evaluate as a binder-free anode for SIBs, the resultant electrode delivers a superior sodium-ion storage capacity of 380mAhg−1 after 150 cycles at 100 mA g−1, a remarkable rate performance and an outstanding long-cycling stability of 129mAhg−1 after 500 cycles at 3.2 A g−1, which is better than other MOFs-derived free-standing anode materials for SIBs reported previously. The 1D carbon fibers can serve as a buffer framework to ensure the structural stability. In addition, the conductive matrix formed by the interleaving of carbon fibers can facilitate electronic transport along their 1D geometry. Furthermore, the dispersed ZIF-67/Co2+ ions derivatives in fibers provide the composite with high surface exposure to the electrolyte, which is conducive to chemical reactions.

Enhanced rate capability of Li4Ti5O12 anode material by a photo-assisted sol–gel route for lithium-ion batteries

Photo-assisted sol–gel route was developed to prepare nanostructured Li4Ti5O12 anode materials. Resulting Li4Ti5O12 powders were characterized by phase analysis, microscopic morphology observation, and cyclic charge/discharge tests. As lithium-ion battery electrode, synthesized Li4Ti5O12 material by using the photo-assisted sol–gel route shows specific capacity of 120 mAh g−1 at 10C discharge rate. Furthermore, this material retains 98% of its initial specific capacity at 0.2C after 50 charge/discharge measurements. Outstanding rate capability and cycling stability of this Li4Ti5O12 material are mainly derived from grain refinement induced by ultraviolet photo-irradiation. Therefore, this photo-assisted sol–gel route is attractive alternative method for preparing electrode materials for high-power lithium-ion battery applications.

Suppressing the interlayer-gliding of layered P3-type K0.5Mn0.7Co0.2Fe0.1O2 cathode materials on electrochemical potassium-ion storage

In recent years, potassium-ion batteries (KIBs) have emerged as a promising alternative candidate to replace lithium-ion batteries for large-scale energy storage devices owing to the natural abundance of potassium and similar mechanism as lithium-ion batteries. In particular, transition metal oxide cathode materials have attracted growing attention due to their high theoretical capacities and low cost compared with other cathode materials. Nevertheless, due to the larger ionic radius of K-ions, transition metal oxide cathode materials suffer from irreversible structural evolution and interlayer-gliding of transition metal layers in potassiation/depotassiation, which results in sluggish kinetics and structural instability. This limited capacity and unsatisfactory cycling properties inhibit the practical application of potassium-ion batteries. It still remains a challenge to develop the suitable cathode materials for potassium-ion batteries. In this work, the interlayer-gliding and irreversible P3–O3 structure transition were suppressed via the replacement of cobalt and iron, and the doping mechanism was investigated by in situ x-ray diffraction. The incorporation of Co ions and Fe ions enlarges the d-space between the transition metal layers, reduces the resistance of K+ migration, and provides the buffer spaces to suppress the interlayer-gliding and P3–O3 phase transformation in electrochemical potassium-ion storage, leading to an enhanced rate capability (58 mA h g−1 at 1 A g−1) and superior cycling stability (71% after 300 cycles at 200 mA g−1). This strategy provides a better understanding for the effect of Co–Fe substitution in suppressing interlayer-gliding and improving electrochemical properties for the development of a novel cathode material for potassium-ion batteries.

One-pot solvothermal preparation of graphene encapsulated SnO nanospheres composites for enhanced lithium storage

SnO based material is one of the most promising anode materials for lithium-ion batteries owing to its high theoretical capacity. However, the difficult synthesis process, large volume expansion and rapid capacity decay, etc., limited its further application. Herein, graphene encapsulated SnO nanospheres, self-assembled from numerous nano-sized secondary nanoparticles, have been successfully synthesized through an efficient one-pot solvothermal method within three hours. The graphene encapsulation and secondary particle assembly structure effectively improves the conductivity of SnO, shortens the ion transmission path and reduces its volume expansion during cycling, thus achieving cycle stability. SnO/G-3 H composite delivers a discharge capacity of 1307 mA h g −1 after 700 cycles at 800 mA g −1 , and maintained an enhanced rate capability of 423 mA h g −1 at 3000 mA g −1 . This simple, economic, and environmental-friendly synthesis route can be extended to the preparation of other transition metal oxide materials.

Synthesis of hierarchical porous CoS2/MWCNTs nanohybrids as electrode for high-performance supercapacitors with enhanced rate capability and cycling stability

Synthesis of hierarchical porous CoS2/MWCNTs nanohybrids as electrode for high-performance supercapacitors with enhanced rate capability and cycling stability

Enhanced rate capability of interconnected LiNi1/3Mn1/3Co1/3O2 nanoparticle cathode

Enhanced rate capability of interconnected LiNi1/3Mn1/3Co1/3O2 (NMC) nanoparticles fabricated via electrospinning method is presented. Interconnected NMC nanoparticles have a discharge capacity of 175 mAh g−1 at 0.1C and 94 mAh g−1 at 1C. Similar nanoparticular NMC cathode without interconnections, fabricated by co-precipitation method, has a capacity of 22 mAh g−1 at 1C. Interconnected NMC nanoparticles have good cycling stability after 500 cycles at 1C with a capacity of ~17 mAh g−1. Though the rate capability of Interconnected NMC nanoparticles is superior, cycling stability is similar across cathodes, indicating that capacity fading is intrinsic to the cathode.

Templated synthesis of nano-LiCoO2 cathode for lithium-Ion batteries with enhanced rate capability

In this work, the nanosized lithium cobalt oxide (LiCoO2) is synthesized by a high-temperature solid-state reaction method using (Zeolitic Imidazolate Framework‐67) as self-sacrificial template. By compared to commercial LiCoO2, the nano LiCoO2 demonstrates high porosity, boosted electrochemical behavior and enhanced specific capacity. As the cathode for lithium ions battery, it delivers a high capacity of 112.3 mAh g−1 over 300 cycles between 3 and 4.5 V at 0.5C. Even at 3C, the specific capacity is 137.5 mAh g−1, which is 62% higher than that of commercial LiCoO2 (84.9 mAh g−1).

V2O5 nanocrystals: Chemical solution synthesis, hydrogen thermal treatment and enhanced rate capability as cathode materials for lithium-ion batteries

Vanadium pentoxide (V2O5) is regarded as a promising cathode material for high-performance lithium-ion batteries (LIBs). In this study, V2O5 nanocrystals with an elongated plate-like morphology are prepared via a chemical solution approach that involves the hydrolyzation of vanadyl sulfate in alkaline solution. Oxygen vacancies are intentionally created by thermal treating the V2O5 samples under hydrogen-containing gases at different temperatures. Although the annealing process does not change the shape, morphology and crystalline structure of V2O5 nanocrystals, it does bring about a small amount of oxygen vacancies, as evidently from the results of XRD patterns and Raman spectra. The presence of oxygen vacancies has positive effects on the electrochemical properties. A higher initial discharge capacity, and excellent rate capability and cycling stability are observed on the oxygen vacancy-containing V2O5 samples. Especially, the sample annealed at 350 °C is found to have an initial capacity of 284 mAh g−1and the capacity still maintains at about 153 mAh g−1 even at 10 C. The combination of nanoscale dimension and oxygen vacancies in V2O5 nanocrystals presents a simple way to improve their rate capability and cycling stability for potential high-performance LIB applications.

Improved zinc-ion storage performance of the metal-free organic anode by the effect of binder

Zinc-ion batteries (ZIBs) using zinc metal as anode materials suffer from Zn dendrite formation and hydrogen evolution during the stripping/plating process, which will lead to performance degradation and hinder practical application. Herein, the 1,4,5,8-naphthalene diimide (NI) is proposed as a promising dendrite-free organic anode material for ZIBs. Moreover, the effect of different binders on electrochemical performance of NI electrode is investigated. Compared NI electrode with polyvinylidene fluoride (PVDF) binder, the NI electrode with the polytetrafluoroethylene (PTFE) binder shows highly enhanced rate capability (122.2 mA h g–1 at 5 A g–1) and cycling performance (123.3 mA h g–1 at 3 A g–1 after 2200 cycles). The improvement cycling stability of NI is attributed to PTFE binder, which effectively maintains electrode structure and inhibits dissolution of organic molecules during the cycling process. In addition, the ion kinetics analyses reveal that the superior rate capability is provided by the capacitive charge storage. And the carbonyl group of NI is active center of electrochemistry, which is revealed by in-situ attenuated total reflection–Fourier transform infrared (ATR-FTIR) and ex-situ Raman. Besides, the aqueous Zn-ion full cell based on metal-free NI anode and Prussian blue analogues (PBAs) cathode exhibits excellent rate capability (113.9 mA h g–1 at 10.0 A g–1), high operation voltage of ~ 1.2 V (at 1.0 A g–1) and energy density of 50.2 Wh kgtotal–1. This work may provide a new design inspiration to develop organic dendrite-free zinc anodes for high-performance aqueous ZIBs batteries.

Lithium-Metal Anodes Working at 60 mA cm-2 and 60 mAh cm-2 through Nanoscale Lithium-Ion Adsorbing.

Achieving high-current-density and high-area-capacity operation of Li metal anodes offers promising opportunities for high-performing next-generation batteries. However, high-rate Li deposition suffers from undesired Li-ion depletion especially at the electrolyte-anode interface, which compromises achievable capacity and lifetime. Here, electronegative graphene quantum dots are synthesized and assembled into an ultra-thin overlayer capable of efficient Li-ion adsorbing at the nanoscale on Li-metal to fully relieve Li-ion depletion. The protected Li anode achieves long-term reversible Li plating/stripping over 1000 h at both superior current density of 60 mA cm-2 and areal capacity of 60 mAh cm-2 . Implementation of the protected anode allows for the construction of Li-air full battery with both enhanced rate capability and cycling performance.

Lithium‐Metal Anodes Working at 60 mA cm−2 and 60 mAh cm−2 through Nanoscale Lithium‐Ion Adsorbing

AbstractAchieving high‐current‐density and high‐area‐capacity operation of Li metal anodes offers promising opportunities for high‐performing next‐generation batteries. However, high‐rate Li deposition suffers from undesired Li‐ion depletion especially at the electrolyte‐anode interface, which compromises achievable capacity and lifetime. Here, electronegative graphene quantum dots are synthesized and assembled into an ultra‐thin overlayer capable of efficient Li‐ion adsorbing at the nanoscale on Li‐metal to fully relieve Li‐ion depletion. The protected Li anode achieves long‐term reversible Li plating/stripping over 1000 h at both superior current density of 60 mA cm−2 and areal capacity of 60 mAh cm−2. Implementation of the protected anode allows for the construction of Li‐air full battery with both enhanced rate capability and cycling performance.

Facile synthesis of layered NiCo2S4/NiO/nickel foam nanoarchitecture as a sophisticated efficient electrode for next-generation supercapacitors

The current study demonstrates the layered nanospheres of NiCo2S4/NiO/NF that were synthesized using the facile and economical chemical bath deposition that was employed as a potential electrode for supercapacitors. Various electrochemical analyses were made using cyclic voltammetry, galvanostatic charge-discharge, potentiostatic electron impedance spectroscopy. The structure, phase, morphology, and chemical composition were examined by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The as-synthesized precursors of electroactive material behavior were illustrated by the three-electrode setup where 3 M KOH was deployed as an electrolyte. The peculiar and unique structural features of the nanoparticles enable and deliver effective pathways for swift electronic and ionic diffusion. Hence, as-synthesized binder-free NCS/NiO/NF showed a dominant specific capacity of 188.03 mA h g−1 at a current density of 1 A g−1, the enhanced rate capability of 80.63%, and the predominant cycling stability of 92.56% over 4000 cycles which are considered an appreciable value than the independent NCS/NF and NiO/NF electrodes. The results in this study portray the fact that the nanocomposite of NCS/NiO/NF establishes an excellent energy storage performance for next-generation supercapacitor applications.

Nanoconfined ReS2 in biomass-derived 3D porous N-doped carbon architecture as anode for stable lithium-ion storage

Rhenium disulfide (ReS2) has emerged as a promissing host material toward energy storage for its distinctive electronic, optical, and mechanical features. Nevertheless, structural damage during repeated charge-discharges and inferior conductivity have severely impaired the electrochemical performance of ReS2. Effective incorporation with carbon component is a feasible pathway to cope with these issues. In this work, employing glucosamine as carbon and nitrogen sources, small ReS2 nanoparticles are easily encapsulated into hierarchical porous N-doped carbon networks to obtain ReS2NC hybrids via a freeze-drying and subsequent annealing method. The hierarchical porous structure and the confining effect of carbon matrix on ReS2 nanoparticles can effectively inhibit the aggregation, maintain the structural stability as well as guarantee the rapid ion diffusion and electron transfer. As a consequence, ReS2NC hybrid anode achieves an extremely improved electrochemical property for lithium-storage. The optimized ReS2NC electrode can remain a high capacity of ~676 mAh g−1 as 500 cycles under 0.1 A g−1 are completed. Besides, as it cycles for 500 loops under 1 A g−1, a capacity of ~387 mAh g−1 is still kept, demonstrating enhanced rate capability.

Mixed Cu2 Se Hexagonal Nanosheets@Co3 Se4 Nanospheres for High-Performance Asymmetric Supercapacitors.

Rational designing and constructing multiphase hybrid electrode materials is an effective method to compensate for the performance defects of the single component. Based on this strategy, Cu2 Se hexagonal nanosheets@Co3 Se4 nanospheres mixed structures have been fabricated by a facile two-step hydrothermal method. Under the synergistic effect of the high ionic conductivity of Cu2 Se and the remarkable cycling stability of Co3 Se4 , Cu2 Se@Co3 Se4 can exhibit outstanding electrochemical performance as a novel electrode material. The as-prepared Cu2 Se@Co3 Se4 electrode displays high specific capacitance of 1005 F g-1 at 1 A g-1 with enhanced rate capability (56 % capacitance retention at 10 A g-1 ), and ultralong lifespan (94.2 % after 10 000 cycles at 20 A g-1 ). An asymmetric supercapacitor is assembled applying the Cu2 Se@Co3 Se4 as anode and graphene as cathode, which delivers a wide work potential window of 1.6 V, high energy density (30.9 Wh kg-1 at 0.74 kW kg-1 ), high power density (21.0 Wh kg-1 at 7.50 kW kg-1 ), and excellent cycling stability (85.8 % after 10 000 cycles at 10 A g-1 ).

On the Optimization of Core-Shell Hybrid Cathode Materials for Extreme Fast-Charging: First Principles Computational Insights

Core-shell and core-gradient hybrid cathode materials for lithium-ion batteries display enhanced rate capability over their homogeneous counterparts. The apparent enhancement of transport is shown to arise from advective flow of Li+ from the higher free-energy core towards the lower free-energy shell compositions. First-principles analysis of a planar model of these hybrid structures concludes that the inbuilt free-energy gradient enhances the Li+ de-intercalation process by reducing the average overpotential during extreme fast-charging. Analysis of representative LiNi0.8Co0.1Mn0.1O2||LiNi0.4Co0.2Mn0.4O2 core/shell reveals: (i) an optimal components ratio exists that maximizes storage capacity during fast-charging and (ii) components should be selected with appreciably large chemical potential difference between the core and shell to further exploit the free-energy gradient effects provided volume ratios are optimized against the potential gradient. In the case of NCM811||NCM424 studied herein, a balanced (ca. 40/60 vol.%) structure appears optimal. This finding indicates that the shell must not necessarily be confined to a thin chemically-protective coating; higher relative volumes of the lower free-energy shell may provide performance benefits at high-rates. The presented insights will serve towards optimizing and developing high capacity, more rate capable core-shell particles for extreme fast charging batteries. Figure 1

Covalent organic frameworks with immobilized anions to liberate lithium ions: Quasi-solid electrolytes with enhanced rate capabilities

Ionic liquids (ILs) are promising candidates as fast Li+ conductors owing to their high ionic conductivity and admirable stability. However, the mobile ions in ILs will contribute to the overall ion conductivity which decreases Li ions transfer efficiency and rate capability of batteries. The improvemnt of Li ions transfer efficiency in ILs electrolyte materials is a great challenge. Covalent organic frameworks (COFs) with high porosity and aligned nanosize channels can offer free flowing pathways for Li+ migration as well as abundant active sites to anchor anions and liberate free Li+, which can maximize Li+ transfer efficiency. Herein we design a cationic COF and a neutral COF as porous hosts for immobilizing the anions of IL N,N-diethyl-N-(2-methoxyethyl)-N-methylammoniumbis(trifluoromethylsulphonyl)imide (DEME-TFSI) to enhance Li+ transference efficiency. The obtained quasi-solid COFs-IL electrolytes exhibit high IL loading amount owing to strong interactions between COFs and the IL. Moreover, COFs-IL electrolytes show good electrochemical stability and high ionic conductivity over 1×10−3 S cm−1, along with a 90% increase of Li+ transfer number in comparison to the bare IL electrolyte (IL/LiTFSI). Our research provides a general strategy for immobilizing mobile anions to liberate Li+ and improve Li+ transfer efficiency in IL-based electrolytes.

Chalcogenide Dopant-Induced Lattice Expansion in Cobalt Vanadium Oxide Nanosheets for Enhanced Supercapacitor Performance

We explore the effect of sulfur doping in Co3V2O8 on the electrochemical performance of supercapacitors in terms of enhanced lattice spacing, electrochemical surface area (ECSA), electronic conductivity, and density of states. The sulfur-doped Co3V2O8 (S-Co3V2O8) nanosheets were grown in situ as a binder-free synthesis on nickel foam by the hydrothermal method. The electrochemical performance was analyzed in an aqueous alkaline electrolyte where the S-Co3V2O8 electrode exhibited a specific capacity of 410 mAh/g at 2 A/g with enhanced rate capability and capacity retention of 94.2% at 5 A/g specific currents after 4000 cycles, whereas the undoped Co3V2O8 electrode exhibited a specific capacity of 337.8 mAh/g at 2 A/g. The high capacity of S-Co3V2O8 is attributed to the enhanced ECSA (by ∼45%) and improved electrical conductivity (by ∼22%) upon doping with sulfur. Furthermore, these results corroborated with density functional theory results. The calculations suggest an increase in lattice parameters and the introduction of additional density of states near the valence-band edge due to the doping of sulfur, resulting in a decrease in charge-transfer resistance. An asymmetric supercapacitor was fabricated, using S-Co3V2O8 nanosheets as the cathode and activated carbon as the anode, which shows a high specific capacity (or capacitance) value of 485 mAh/g, an energy density of 36.4 W h/kg, and a power density of 740 W/kg at 2 A/g with 98.4% specific capacity retention after 4000 consecutive charge–discharge cycles. Furthermore, the analysis was extended in a nonaqueous medium for Li-ion storage where S-Co3V2O8 exhibits a specific capacity of 994 mA h/g and a specific energy density of 828 W h/kg at 1 A/g making it a promising candidate for future high-energy storage systems. The concept of doping is extended to other chalcogenide (e.g., selenium) doping (Se-Co3V2O8), which also shows improved device performance and makes this a versatile approach for high-performance devices.

Coating Porous MXene Films with Tunable Porosity for High‐Performance Solid‐State Supercapacitors

AbstractTwo‐dimensional MXenes with their outstanding physical and chemical properties have been extensively used in numerous fields such as electrochemical energy storage, catalysis, and sensing. In these applications, high active surface area and facilitated diffusion of ions/atoms/molecules are crucial. While these features can be offered by porous films and structures, their fabrication at ambient conditions, especially with scalable methods such as printing and coating has proven to be quite challenging. Here, we have developed MXene inks containing a space‐holder agent, based on which porous films with tunable porosities can be easily coated. The whole fabrication process lasts only a few minutes and is carried out at room temperature and pressure, making it suitable for continuous scalable production. Films with different porosities (up to 80 %) have been coated and used for the fabrication of solid‐state microsupercapacitors with enhanced rate capability and improved capacitance (241 mF/cm2).

SnS nanoparticles anchored on nitrogen-doped carbon sheets derived from metal-organic-framework precursors as anodes with enhanced electrochemical sodium ions storage

Tin monosulfide (SnS) has emerged as a promissing host material toward sodium-storage for its low cost and high capacity. Nevertheless, unavoidable capacity fading as well as poor rate capability have severely hindered the extended practical application of SnS. Carbon coating is an effective strategy to address these issues. In this paper, a SnS coupled with nitrogen-doped carbon hybrid (SnS/NCS) has been fabricated through an easy template method with a 2D tin-based metal organic framework (Sn-MOF) as precursor. By an annealing and sulfuration treatment, ultrasmall SnS nanoparticles are well in-situ formed and embedded onto MOF-derived nitrogen-doped carbon sheets. Conductive carbon components can provide electron expressway and robust mechanical support. Furthermore, the confining effect of carbon matrix on SnS nanoparticles effectively alleviates the volume expansion. Having profited from the desirable nanostructures, SnS/NCS anode achieves an extremely improved electrochemical property for sodium-storage. At the end of 150 cycles under a current density of 100 mA g−1, SnS/NCS remains a high capacity of ~522 mAh g−1. Besides, even at a large current density of 1000 mA g−1, SnS/NCS still keeps a capacity of ~321 mAh g−1 after finishing 200 cycles of test and achieves an enhanced rate capability.