RESUMEN
Hosts hold great prospects for addressing the dendrite growth and volume expansion of the Li metal anode, but Li dendrites are still observable under the conditions of high deposition capacity and/or high current density. Herein, a nitrogen-doped graphene mesh (NGM) is developed, which possesses a conductive and lithiophilic scaffold for efficient Li deposition. The abundant nanopores in NGM can not only provide sufficient room for Li deposition, but also speed up Li ion transport to achieve a high-rate capability. Moreover, the evenly distributed N dopants on the NGM can guide the uniform nucleation of Li so that to inhibit dendrite growth. As a result, the composite NGM@Li anode shows satisfactory electrochemical performances for Li-S batteries, including a high capacity of 600 mAh g-1 after 300 cycles at 1 C and a rate capacity of 438 mAh g-1 at 3 C. This work provides a new avenue for the fabrication of graphene-based hosts with large areal capacity and high-rate capability for Li metal batteries.
RESUMEN
Pseudocapacitors bridge the performance gap between batteries and electric double-layer capacitors by storing energy via a combination of fast surface/near-surface Faradaic redox processes and electrical double-layer capacitance. Organic semiconductors are an emerging class of pseudocapacitive materials that benefit from facile synthetic tunability and mixed ionic-electronic conduction. Reported examples are mostly limited to p-type (electron-donating) conjugated polymers, while n-type (electron-accepting) examples remain comparatively underexplored. This work introduces a new cross-linked n-type conjugated polymer, spiro-NDI-N, strategically designed with polar tertiary amine side chains. This molecular design aims to synergistically increase the electroactive surface area and boost ion transport for efficient ionic-electronic coupling. Spiro-NDI-N demonstrates excellent pseudocapacitive energy storage performance in pH-neutral aqueous electrolytes, with specific capacitance values of up to 532 F g-1 at 5 A g-1 and stable cycling over 5000 cycles. Moreover, it maintains a rate capability of 307 F g-1 at 350 A g-1. The superior pseudocapacitive performance of spiro-NDI-N, compared to strategically designed structural analogues lacking either the cross-linked backbone or polar side chains, validates the essential role of its molecular design elements. More broadly, the design and performance of spiro-NDI-N provide a novel strategy for developing high-performance organic pseudocapacitors.
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Currently, a major target in the development of Na-ion batteries is the concurrent attainment of high-rate capacity and long cycling stability. Herein, an advanced Na-ion battery with high-rate capability and long cycle stability based on Li/Ti co-doped P2-type Na0.67Mn0.67Ni0.33O2, a host material with high-voltage zero-phase transition behavior and fast Na+ migration/conductivity during dynamic de-embedding process, is constructed. Experimental results and theoretical calculations reveal that the two-element doping strategy promotes a mutually reinforcing effect, which greatly facilitates the transfer capability of Na+. The cation Ti4+ doping is a dominant high voltage, significantly elevating the operation voltage to 4.4 V. Meanwhile, doping Li+ shows the function in charge transfer, improving the rate performance and prolonging cycling lifespan. Consequently, the designed P2-Na0.75Mn0.54Ni0.27Li0.14Ti0.05O2 cathode material exhibits discharge capacities of 129, 104, and 85 mAh g- 1 under high voltage of 4.4 V at 1, 10, and 20 C, respectively. More importantly, the full-cell delivers a high initial capacity of 198 mAh g-1 at 0.1 C (17.3 mA g-1) and a capacity retention of 73% at 5 C (865 mA g-1) after 1000 cycles, which is seldom witnessed in previous reports, emphasizing their potential applications in advanced energy storage.
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An electronically conjugated functional triazine framework is used to synthesize a physicochemically interlocked sulfur cathode that delivers high energy density coupled with exceptional cycle life in lithium-sulfur batteries. Conventional melt-diffusion strategies to impregnate sulfur in the cathode offer poor cycle life due to physical mixing with weak interactions. By contrast, in this approach, sulfur is physicochemically entrapped within a nanoporous and heteroatom doped high surface area covalent triazine framework, resulting in outstanding electrochemical performance (≈89% capacity retention after 1000 cycles, the energy density of ≈2,022 Wh kg-1 sulfur and high-rate capability up to 12 C). The overall structural characteristics and interactions of sulfur with the covalent triazine framework are explored in detail to explain the intriguing properties of the sulfur cathode.
RESUMEN
Chloride-ion batteries (CIBs) have drawn growing attention in large-scale energy storage applications owing to their comprehensive merits of high theoretical energy density, dendrite-free characteristic, and abundance of chloride-containing materials. Nonetheless, cathodes for CIBs are plagued by distinct volume effect and sluggish Cl- diffusion kinetics, leading to inferior rate capability and short cycling life. Herein, an unconventional Ni5 Ti-Cl LDH is reported with a high nickel ratio as a cathode material for CIB. The reversible capacity of Ni5 Ti-Cl LDH retains 127.9 mAh g-1 over 1000 cycles at a large current density of 1000 mA g-1 , which exceeds that of ever reported CIBs, with extraordinary low volume change of 1.006% during a whole charge/discharge process. Such superior Cl-storage performance is attributed to synergetic contributions consisting of high redox activity from Ni2+ /Ni3+ and pinning Ti that restrains local structural distortion of LDH host layers and enhances adsorption intensity of chloride atoms during the reversible Cl- intercalation/de-intercalation in LDH gallery, which are revealed by a comprehensive study including X-ray photoelectron spectroscopy, kinetic investigations, and DFT calculations. This work provides an effective strategy to design low-cost LDHs materials for high-performance CIBs, which are also applicable to other types of halide-ion batteries (e.g., fluoride-ion and bromide-ion batteries).
RESUMEN
Electrochemical sodium-ion storage technologies have become an indispensable part in the field of large-scale energy storage systems owing to the widespread and low-cost sodium resources. Molybdenum carbides with high electron conductivity are regarded as potential sodium storage anode materials, but the comprehensive sodium storage mechanism has not been studied in depth. Herein, Mo2 C nanowires (MC-NWs) in which Mo2 C nanoparticles are embedded in carbon substrate are synthesized. The sodium-ion storage mechanism is further systematically studied by in/ex situ experimental characterizations and diffusion kinetics analysis. Briefly, it is discovered that a faradaic redox reaction occurs in the surface amorphous molybdenum oxides on Mo2 C nanoparticles, while the inner Mo2 C is unreactive. Thus, the as-synthesized MC-NWs with surface pseudocapacitance display excellent rate capability (a high specific capacity of 76.5 mAh g-1 at 20 A g-1 ) and long cycling stability (a high specific capacity of 331.2 mAh g-1 at 1 A g-1 over 1500 cycles). The assembled original sodium ion capacitor displays remarkable power density and energy density. This work provides a comprehensive understanding of the sodium storage mechanism of Mo2 C materials, and constructing pseudocapacitive materials is an effective way to achieve sodium-ion storage devices with high power and energy density.
RESUMEN
Structure engineering of electrode materials can significantly improve the life cycle and rate capability of the sodium-ion battery (SIB), yet remains a challenging task due to the lack of an effective synthetic strategy. Herein, the microstructure of VS4 hollow spheres is successfully engineered through a facile hydrothermal method. The hollow VS4 microspheres possess rich porosity and are covered with 2D ultrathin nanosheets on the surface. The finite element simulation (FES) reveals that such heterostructures can effectively relieve the stress induced by the sodiation and thereby enhance the structural integrity. The SIB with the hollow VS4 microspheres as anode displays impressively high specific capacity, excellent stability upon ultra-long cycling, and extraordinary rate capacity, e.g., a reversible capacity of ≈378 mA h g-1 at ultra-high 10 A g-1 , while retaining 73.2% capacity after 1000 cycles. The Na storage mechanism is also elucidated through in situ/ex situ characterizations. Moreover, the hollow VS4 microspheres demonstrate reliable rate performance at a low temperature of -40 °C (e.g., the capacity is ≈163 mA h g-1 at 2 A g-1 ). This work provides novel insights toward high-performance SIBs.
RESUMEN
Ni-Co binary hydroxide (NixCo1-x(OH)2) with nanostructure is prepared by one-step electrochemical deposition process with de-ionized water as electrolyte. The molar ratio of Ni/Co for NixCo1-x(OH)2can be accurately controlled via changing the composition of the alloy target. A series of typical hydroxides are synthesized with Ni/Co molar ratios of 1:2, 1:3, 1:4, 1:6, 6:1, 4:1, 3:1, 2:1 and 1:1. The electrochemical performances of NixCo1-x(OH)2exhibit remarkable improvement in rate capability and cycling stability compared to monometallic hydroxide. Electrochemical test results reveal that Ni4/5Co1/5(OH)2delivers the maximum specific capacitance of 2425 F g-1, while Ni0.5Co0.5(OH)2exhibits ultrahigh rate capability (a 14% capacity decrease after a 100-fold increase in scan rate and 7% capacity decrease after a 40-fold increase in current density) and super-long cycle life (no capacitance loss after 50 000 cycles). Especially, the Ni0.5Co0.5(OH)2//AC supercapacitor exhibits a super-long cycle life with a 2% capacitance loss after 100 000 cycles, which is quite better than that of crystalline devices.
RESUMEN
Aqueous asymmetric supercapacitor has captured widespread attention as a sustainable high-power energy resource. Organic electrode materials are appealing owing to their sustainability and high redox reactivity, but suffer from structural instability and low power density. Here the π-conjugated polyimide-based organic electrodes with different lengths of alkyl chains are explored to achieve high rate capability and long lifespan in an aqueous K+ -ion electrolyte. The fabricated asymmetric supercapacitor exhibits high capacities of 107 mAh g-1 at 2 A g-1 and 67 mAh g-1 at 90 A g-1 . A specific capacity of 65 mAh g-1 over 70% of the initial performance is obtained after 65â¯000 cycles. Molecular engineering of long alkyl chains in polyimide can reduce the degree of π-conjugation and spatially block the π-conjugated imide bond with limited redox activity but improved stability against chemical degradation. Further electrochemical quartz crystal microbalance, ex-situ Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations reveal the pseudocapacitance behavior originating from the π-conjugated polyimide-based redox reaction with potassium ions and hydrated potassium ions. A promising polyimide-based polymer with extended π-conjugated system for high-performance asymmetric supercapacitor is showcased.
RESUMEN
Sodium- and potassium-ion batteries have attracted intensive attention recently as low-cost alternatives to lithium-ion batteries with naturally abundant resources. However, the large ionic radii of Na+ and K+ render their slow mobility, leading to sluggish diffusion in host materials. Herein, hierarchical FeSe2 microspheres assembled by closely packed nano/microrods are rationally designed and synthesized through a facile solvothermal method. Without carbonaceous material incorporation, the electrode delivers a reversible Na+ storage capacity of 559â mA h g-1 at a current rate of 0.1â A g-1 and a remarkable rate performance with a capacity of 525â mA h g-1 at 20â A g-1 . As for K+ storage, the FeSe2 anode delivers a high reversible capacity of 393â mA h g-1 at 0.4â A g-1 . Even at a high current rate of 5â A g-1 , a discharge capacity of 322â mA h g-1 can be achieved, which is among the best high-rate anodes for K+ storage. The excellent electrochemical performance can be attributed to the favorable morphological structure and the use of an ether-based electrolyte during cycling. Moreover, quantitative study suggests a strong pseudocapacitive contribution, which boosts fast kinetics and interfacial storage.
RESUMEN
Both poor electron conductivity and low ion diffusion of electrode materials are two main issues limiting the rate performance of pseudocapacitors. The present work reports the design and fabrication of hierarchically nano-architectured electrodes consisting of sulfide vacancies enhanced Ni-Co-S nanoparticle covering bent nickel nano-forest (BNNF). We propose new insight into vastly increased ion-accessible active sites and fast charge storage/delivery enhanced the reaction kinetics. The Ni-Co-S@BNNF electrode exhibits extremely high rate performance with 90.1% capacity retention from 1 to 20 A g-1, and even still remains 83.6% capacity at 40 A g-1, much superior to reported NiCo2S4-based electrodes. The high rate performance is attributed to the unique nano-architecture providing increased ion availability of electrochemically active sites and high conductivity for fast electron transport. Especially the electrode achieves remarkable long-term cycle stability with more than 100% initial capacity value after 5000 cycles at 5 A g-1and exhibits excellent cycle reversibility even at 20 A g-1. Goog cycle stability should be attributed to the sulfide vacancies in Ni-Co-S nano-branches and the electrode architecture sustaining structural strain during fast redox reactions. An asymmetric pseudocapacitor applying such electrode achieves a high energy density of 99.9 W h kg-1and exhibits superior cycling stability at a high current density of 20 A g-1. This study underscores the potential importance of developing nanoarrays covered with highly redox-active materials with increasing ions/charge kinetics for energy storage.
RESUMEN
Slow ion kinetics of negative electrode materials is the main factor of limiting fast charge and discharge of batteries. Sluggish Na+ kinetics property leads to large electrode polarization, resulting in poor rate and cyclic performances. Herein, an electrode of ultrasmall tin nanoparticles decorated in N, S codoped carbon monolith (TCM) with exceptional high-rate capability and ultrastable cycling behavior for Na-storage is reported. The resulted TCM electrode exhibits an extremely high retention of 96% initial charge capacity after 500 cycles at a current density of 500 mA g-1 . Significantly, when the current density is elevated to an ultrahigh rate of 5000 mA g-1 , a high reversible capacity of 228 mAh g-1 after the 2000th cycle is still maintained. More importantly, the stable and fast Na-storage of TCM is investigated and understood by experimental characterizations and kinetics calculations, including interfacial ion/electron transport behavior, ion diffusion, and quantitative pseudocapacitive analysis. These investigations elucidate that the TCM shows improved ion/electron conductivity and enhanced interfacial kinetics. An entirely new perspective to deep insights into the fast ion/electron transport mechanisms revealed by interfacial kinetics of sodiation/desodiation, which contributes to the profound understanding for developing fast charging/discharging and long-term stable electrodes in sodium-ion batteries, is provided.
RESUMEN
Rechargeable Zn-ion batteries are promising candidates for wearable energy storage devices. However, their performance is severely restricted by the low conductivity and inferior mass loading. Herein, a new type of the textile based electrodes with 3D hierarchical branched design is reported. Both Ni nanoparticles and carbon nanotubes are used to build conductive coatings on the textiles. The 3D hierarchical nanostructures, consisting of the vertical-aligned nanosheets and the fluffy-like small flakes, grow on the conductive textiles to form the self-supported electrodes. It ensures fast electron/ion transport and high mass loading, and maintains the structure stability during cycling. Two textile electrodes with the NiCo hydroxide and MnO2 self-branched nanostructures are constructed. Their faster kinetics, higher capacity and better rate capability than the solitary nanosheets based counterpart demonstrate the superiority of the hierarchical architecture. Moreover, the solid-state Zn-MnO2 and Zn-NiCo batteries are fabricated based on the textile electrodes and the polymer electrolytes. The high energy density, superior power density and good long-term cycling stability confirm their excellent energy storage ability and fast charge/discharge capability. Particularly, the high safety under various conditions enable them promising candidates for wearable electronics.
RESUMEN
Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at -20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation.
RESUMEN
Transition metal chalcogenide with tailored nanosheet architectures with reduced graphene oxide (rGO) for high performance electrochemical sodium ion batteries (SIBs) are presented. Via one-step oriented attachment growth, a facile synthesis of Co9 Se8 nanosheets anchored on rGO matrix nanocomposites is demonstrated. As effective anode materials of SIBs, Co9 Se8 /rGO nanocomposites can deliver a highly reversible capacity of 406 mA h g-1 at a current density of 50 mA g-1 with long cycle stability. It can also deliver a high specific capacity of 295 mA h g-1 at a high current density of 5 A g-1 indicating its high rate capability. Furthermore, ex situ transmission electron microscopy observations provide insight into the reaction path of nontopotactic conversion in the hybrid anode, revealing the highly reversible conversion directly between the hybrid Co9 Se8 /rGO and Co nanoparticles/Na2 Se matrix during the sodiation/desodiation process. In addition, it is experimentally demonstrated that rGO plays significant roles in both controllable growth and electrochemical conversion processes, which can not only modulate the morphology of the product but also tune the sodium storage performance. The investigation on hybrid Co9 Se8 /rGO nanosheets as SIBs anode may shed light on designing new metal chalcogenide materials for high energy storage system.
RESUMEN
Constructing heterostructures can endow materials with fascinating performance in high-speed electronics, optoelectronics, and other applications owing to the built-in charge-transfer driving force, which is of benefit to the specific charge-transfer kinetics. Rational design and controllable synthesis of nano-heterostructure anode materials with high-rate performance, however, still remains a great challenge. Herein, ultrafine SnS/SnO2 heterostructures were successfully fabricated and showed enhanced charge-transfer capability. The mobility enhancement is attributed to the interface effect of heterostructures, which induces an electric field within the nanocrystals, giving them much lower ion-diffusion resistance and facilitating interfacial electron transport.
RESUMEN
LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently "plagued" by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of â¼ 155 mAh/g, â¼ 135 mAh/g, and â¼ 125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of â¼ 70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was â¼ 30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries.
RESUMEN
A subclass of organic semiconductors known as conjugated polyelectrolytes (CPEs) is characterized by a conjugated backbone with ionic pendant groups. The water solubility of CPEs typically hinders applications of thin films in aqueous media. Herein, it is reported that films of an anionic CPE, namely CPE-K, drop cast from water produces single-component solid-state pseudocapacitive electrodes that are insoluble in aqueous electrolyte. That X-ray diffraction experiments reveal a more structurally ordered film, relative to the as-obtained powder from chemical synthesis, and dynamic light scattering measurements show an increase in aggregate particle size with increasing [KCl] indicate that CPE-K films are insoluble because of tight interchain contacts and electrostatic screening by the electrolyte. CPE-K film electrodes can maintain 85% of their original capacitance (84 F g-1 ) at 500 A g-1 and exhibit excellent cycling stability, where a capacitance retention of 93% after 100 000 cycles at a current density of 35 A g-1 . These findings demonstrate that it is possible to use initially water soluble ionic-organic materials in aqueous electrolytes, by increasing the electrolyte concentration. This strategy can be applied to the application of conjugated polyelectrolytes in batteries, organic electrochemical transistors, and electrochemical sensors, where fast electron and ion transport are required.
RESUMEN
Rechargeable sodium metal batteries are considered to be one of the most promising high energy density and cost-effective electrochemical energy storage systems. However, their practicality is constrained by the high reactivity of sodium metal anodes that readily brings about excessive accumulation of inactive Na species on the surface, either by chemical reactions with oxygen and moisture during electrode handling or through electrochemical processes with electrolytes during battery operation. Herein, this paper reports on an alkali, salt-assisted, assembly-polymerization strategy to recover Na activity and to reinforce the solid-electrolyte interphase (SEI) of sodium metal anodes. To achieve this, an alkali-reactive coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) is applied to convert inactive Na species into Si-O-Na coordination with a self-assembly GPTMS layer that consists of inner O-Si-O networks and outer hydrophobic epoxides. As a result, the electrochemical activity of Na metal anodes can be fully recovered and the robust GPTMS-derived SEI layer ensures high capacity and long-term cycling under an ultrahigh rate of 30 C (93.1 mAh g-1, 94.8% after 3000 cycles). This novel process provides surface engineering clues on designing high power density and cost-effective alkaline metal batteries.
RESUMEN
For rechargeable aqueous zinc-ion batteries (ZIBs), manganese dioxide is one of the most promising candidates as a cathode material because of its cost effectiveness, eco-friendliness, and high specific capacities. However, the ZIBs suffer from poor rate performance and low cycle life due to the weak intrinsic electronic conductivity of manganese dioxide, poor ion diffusion of lump manganese dioxide, and its volumetric expansion during the cycle. Herein, we prepare MnO2@carbon composites (MnO2@IPHCSs) by in situ growing MnO2 nanoflowers on an interconnected porous hollow carbon spheres (IPHCSs) template. IPHCSs, as excellent conductors, significantly improve the conductivity of the manganese dioxide cathode. The hollow porous carbon framework of IPHCSs can offer more ion diffusion paths to internal MnO2@IPHCS carbon composites and acts as a buffer room to cope with the drastic volume contraction and expansion during charge/discharge cycling. The rate performance tests show that MnO2@IPHCSs with high conductivity have a specific capacity of 147 mA h g-1 at 3 C. MnO2@IPHCSs with hollow and nanoflower structures are shown to have excellent ion diffusion performance (ion diffusion coefficient = 10-11 to 10-10 cm2 s-1) in the electrochemical kinetics of the galvanostatic intermittent titration technique. Long cycle performance testing and in situ Raman characterization reveal that MnO2@IPHCSs have high cycling stability (85.5% capacity retention after 800 cycles) and reversibility due to the enhanced structure and increased conductivity. The excellently conductive manganese dioxide supported by IPHCSs has good rate and cycling performance, which can be used to produce superior-performance ZIBs.