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1.
    
The most promising cathode materials, including LiCoO2 (layered), LiMn2O4 (spinel), and LiFePO4 (olivine), have been the focus of intense research to develop rechargeable lithium‐ion batteries (LIBs) for portable electronic devices. Sluggish lithium diffusion, however, and unsatisfactory long‐term cycling performance still limit the development of present LIBs for several applications, such as plug‐in/hybrid electric vehicles. Motivated by the success of graphene and novel 2D materials with unique physical and chemical properties, herein, a simple shear‐assisted mechanical exfoliation method to synthesize few‐layered nanosheets of LiCoO2, LiMn2O4, and LiFePO4 is used. Importantly, these as‐prepared nanosheets with preferred orientations and optimized stable structures exhibit excellent C‐rate capability and long‐term cycling performance with much reduced volume expansion during cycling. In particular, the zero‐strain insertion phenomenon could be achieved in 2–3 such layers of LiCoO2 electrode materials, which could open up a new way to the further development of next‐generation long‐life and high‐rate batteries.  相似文献   

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Among the various energy solutions, lithium‐ion batteries (LIBs) play an important role in the process of the transition from fossil fuels to renewables. However, the necessity to replace lithium with cheaper alternatives due to its scarcity has recently attracted great interest to developing sodium‐ion batteries (SIBs). Hence, the discovery and development of suitable cathode materials that exhibit high specific capacity, good cycling stability, and high energy density are actively pursued. Today's SIB technology continues to be driven by the performance of the cathode materials. Here, recent advancements made regarding the cathode of SIBs are summarized, covering some of the fundamental aspects of SIBs, synthetic protocols, and characteristics of existing and prospective cathode materials used for SIBs. Furthermore, some of the latest achievements in the fabrication of cathode materials, as a practical demonstration on their viability, are also discussed. With better understanding of these topics, the rationales behind their enhanced electrochemical performances are revealed and explained. Last but not least, imminent challenges and future prospects are also included to provide some insights into the possible development of advanced cathode materials for SIBs.  相似文献   

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Magnesium batteries have the potential to be a next generation battery with large capability and high safety, owing to the high abundance, great volumetric energy density, and reversible dendrite‐free capability of Mg anodes. However, the lack of a stable high‐voltage electrolyte, and the sluggish Mg‐ion diffusion in lattices and through interfaces limit the practical uses of Mg batteries. Herein, a spinel MgIn2S4 microflower‐like material assembled by 2D‐ultrathin (≈5.0 nm) nanosheets is reported and first used as a cathode material for high‐temperature Mg batteries with an ionic liquid electrolyte. The nonflammable ionic liquid electrolyte ensure the safety under high temperatures. As prepared MgIn2S4 exhibits wide‐temperature‐range adaptability (50–150 °C), ultrahigh capacity (≈500 mAh g?1 under 1.2 V vs Mg/Mg2+), fast Mg2+ diffusibility (≈2.0 × 10?8 cm2 s?1), and excellent cyclability (without capacity decay after 450 cycles). These excellent electrochemical properties are due to the fast kinetics of magnesium by the 2D nanosheets spinel structure and safe high‐temperature operation environment. From ex situ X‐ray diffraction and transmission electron microscopy measurements, a conversion reaction of the Mg2+ storage mechanism is found. The excellent performance and superior security make it promising in high‐temperature batteries for practical applications.  相似文献   

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Controlling the arrangement and interface of nanoparticles is essential to achieve good transfer of charge, heat, or mechanical load. This is particularly challenging in systems requiring hybrid nanoparticle mixtures such as combinations of organic and inorganic materials. This work presents a process to coat vertically aligned carbon nanotube (CNT) forests with metal oxide nanoparticles using microwave‐assisted hydrothermal synthesis. Hydrothermal processes normally damage delicate CNT forests, which is addressed here by a combination of lithographic patterning, transfer printing, and reduction of the synthesis time. This process is applied for the fabrication of structured Li‐ion battery (LIB) electrodes where the aligned CNTs provide a straight electron transport path through the electrode and the hydrothermal coating process is used to coat the CNTs with conversion anode materials for LIBs. These nanoparticles are anchored on the surface of the CNTs and batteries fabricated following this process show a fourfold longer cyclability. Finally, this process is used to create thick electrodes (350 µm) with a gravimetric capacity of over 900 mAh g?1.  相似文献   

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Sodium‐ion batteries (SIBs) have been considered as potential candidates for stationary energy storage because of the low cost and wide availability of Na sources. O3‐type layered oxides have been considered as one of the most promising cathodes for SIBs. However, they commonly show inevitable complicated phase transitions and sluggish kinetics, incurring rapid capacity decline and poor rate capability. Here, a series of sodium‐sufficient O3‐type NaNi0.5Mn0.5‐ x Ti x O2 (0 ≤ x ≤ 0.5) cathodes for SIBs is reported and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of in situ X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and scanning transmission electron microscopy for NaNi0.5Mn0.2Ti0.3O2 reveals that the O3‐type phase transforms reversibly into a P3‐type phase upon Na+ deintercalation/intercalation. The substitution of Ti for Mn enlarges interslab distance and could restrain the unfavorable and irreversible multiphase transformation in the high voltage regions that is usually observed in O3‐type NaNi0.5Mn0.5O2, resulting in improved Na cell performance. This integration of macroscale and atomicscale engineering strategy might open up the modulation of the chemical and physical properties in layered oxides and grasp new insight into the optimal design of high‐performance cathode materials for SIBs.  相似文献   

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3D hierarchical flower‐like carbon coated MoO3−x nanosheets (denoted as MoO3−x NS@C) have been successfully fabricated by a simple hydrothermal method. When used as anode for Li‐ion batteries, the MoO3−x NS@C electrode exhibits excellent cycle performance and outstanding rate capabilities. The charge capacity can reach 1025 mAh g−1 over 150 cycles, and 62% of the charge capacity is retained when the current density increases to 2000 mA g−1. The improved lithium storage performance of MoO3−x NS@C is attributed to the synergistic effect of oxygen vacancies and the carbon coating, which not only enhance the electric conductivity and Li‐ion diffusion coefficient but also lead to superior structural stability and cyclability of the MoO3−x NS@C electrode during repeated lithiation/delithiation process.  相似文献   

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This study describes preparation of metal sulfide counter electrodes (CEs) through one‐pot microwave‐assisted route to improve power conversion efficiency (PCE) of quantum dot‐sensitized solar cells at a lower cost. The CuS nanorods, Ni0.96S nanoparticles, and PbS nanocubes are synthesized and deposited in situ on fluorine‐doped tin oxide substrate to serve as CEs without further post‐treatment. Effects of several reaction parameters including sulfur precursor (Na2S, C2H5NS, CH4N2S), Cu concentration, reaction time, and choice of cation (Cu, Ni, Pb) on the CEs morphology, electrochemical characteristics, and PCE are studied. Furthermore, nanostructure formation and thin film growth are studied and correlated with PCE, from which morphology‐ and composition‐performance relationships can be inferred. Hierarchically assembled nanorod CuS CEs exhibit higher electrochemical stability in the S2–/Sn2– redox reaction. Together with the efficient charge transfer and higher diffusion coefficient of polysulfide redox at the electrode/electrolyte interface, deduced from electrochemical impedance spectroscopy and Tafel analyses, a PCE of 8.32% is achieved for the CuS CE. The enhanced photovoltaic performance is ascribed to the 1D CuS nanorods forming a diffusive structure which decreases charge transfer impedance and facilitates regeneration of polysulfide redox leading to a higher short‐circuit current density and fill factor.  相似文献   

12.
    
Aqueous rechargeable Zn/birnessite batteries have recently attracted extensive attention for energy storage system because of their low cost and high safety. However, the reaction mechanism of the birnessite cathode in aqueous electrolytes and the cathode structure degradation mechanics still remain elusive and controversial. In this work, it is found that solvation water molecules coordinated to Zn2+ are coinserted into birnessite lattice structure contributing to Zn2+ diffusion. However, the birnessite will suffer from hydroxylation and Mn dissolution with too much solvated water coinsertion. Through engineering Zn2+ primary solvation sheath with strong‐field ligand in aqueous electrolyte, highly reversible [Zn(H2O)2]2+ complex intercalation/extraction into/from birnessite cathode is obtained. Cathode–electrolyte interface suppressing the Mn dissolution also forms. The Zn metal anode also shows high reversibility without formation of “death‐zinc” and detrimental dendrite. A full cell coupled with birnessite cathode and Zn metal anode delivers a discharge capacity of 270 mAh g?1, a high energy density of 280 Wh kg?1 (based on total mass of cathode and anode active materials), and capacity retention of 90% over 5000 cycles.  相似文献   

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Owing to the advantages of high safety, low cost, high theoretical volumetric capacities, and environmental friendliness, magnesium‐ion batteries (MIBs) have more feasibility for large‐scale energy storage compared to lithium‐ion batteries. However, lack of suitable cathode materials due to sluggish kinetics of magnesium ion is one of the biggest challenges. Herein, water‐pillared sodium vanadium bronze nanowires (Na2V6O16·1.63H2O) are reported as cathode material for MIBs, which display high performance in magnesium storage. The hydrated sodium ions provide excellent structural stability. The charge shielding effect of lattice water enables fast Mg2+ diffusion. It exhibits high specific capacity of 175 mAh g?1, long cycle life (450 cycles), and high coulombic efficiency (≈100%). At high current density of 200 mA g?1, the capacity retention is up to 71% even after 450 cycles (compared to the highest capacity), demonstrating excellent long‐term cycling performance. The nature of charge storage kinetics is explored. Furthermore, a highly reversible structure change during the electrochemical process is proved by comprehensive electrochemical analysis. The remarkable electrochemical performance makes Na2V6O16·1.63H2O a promising cathode material for low‐cost and safe MIBs.  相似文献   

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The fast development of electrochemical energy storage devices necessitates rational design of the high‐performance electrode materials and systematic and deep understanding of the intrinsic energy storage processes. Herein, the preintercalation general strategy of alkali ions (A = Li+, Na+, K+) into titanium dioxide (A‐TO, LTO, NTO, KTO) is proposed to improve the structural stability of anode materials for sodium and lithium storage. The different optimization effects of preintercalated alkali ions on electrochemical properties are studied systematically. Impressively, the three electrode materials manifest totally different capacities and capacity retention. The efficiency of the energy storage process is affected not only by the distinctive structure but also by the suitable interlayer spacing of Ti‐O, as well as by the interaction effect between the host Ti‐O layer and alien cations with proper size, demonstrating the pivotal role of the sodium ions. The greatly enhanced electrochemical performance confirms the importance of rational engineering and synthesis of advanced electrode materials with the preintercalation of proper alkali cations.  相似文献   

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The realizing of high‐performance rechargeable aqueous zinc‐ion batteries (ZIBs) with high energy density and long cycling life is promising but still challenging due to the lack of suitable layered cathode materials. The work reports the excellent zinc‐ion storage performance as‐observed in few‐layered ultrathin VSe2 nanosheets with a two‐step Zn2+ intercalation/de‐intercalation mechanism verified by ex situ X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) characterizations. The VSe2 nanosheets exhibit a discharge plateau at 1.0–0.7 V, a specific capacity of 131.8 mAh g?1 (at 0.1 A g?1), and a high energy density of 107.3 Wh kg?1 (at a power density of 81.2 W kg?1). More importantly, outstanding cycle stability (capacity retention of 80.8% after 500 cycles) without any activation process is achieved. Such a prominent cyclic stability should be attributed to its fast Zn2+ diffusion kinetics (DZn2+ ≈ 10?8 cm?2 s?1) and robust structural/crystalline stability. Density functional theory (DFT) calculation further reveals a strong metallic characteristic and optimal zinc‐ion diffusion pathway with a hopping energy barrier of 0.91 eV. The present finding implies that 2D ultrathin VSe2 is a very promising cathode material in ZIBs with remarkable battery performance superior to other layered transitional metal dichalcogenides.  相似文献   

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All‐solid‐state batteries attract significant attention owing to their potential to realize an energy storage system with high safety and energy density. In this paper, a mechanochemical synthesis of novel amorphous positive electrode materials of the Ni‐rich LiNi1−x−yMnxCoyO2 (NMC)–Li2SO4 system suitable for oxide‐type all‐solid‐state batteries is reported. Through the mechanochemical treatment with Li2SO4, excellent formabilities of the electrode materials as those of ductile solid electrolytes are obtained. Owing to the deformability of the active material, a good electrode/electrolyte interface is provided simply by pressing at room temperature. In all‐oxide solid‐state cells using 80NMCs·20Li2SO4 (mol%) positive electrode materials, the cell capacity increases with the Ni content in the NMC. The all‐solid‐state cell using the 80NMC811·20Li2SO4 positive electrode active material exhibits a high capacity larger than 250 mAh g−1 in a voltage range of 1.6–4.8 V versus Li at 100 °C. Furthermore, bulk‐type all‐oxide solid‐state batteries (Li4Ti5O12/80NMC532·20Li2SO4 (mol%)) successfully function as secondary batteries with excellent cycle performances.  相似文献   

18.
    
Rechargeable Zn/MnO2 batteries using mild aqueous electrolytes are attracting extensive attention due to their low cost, high safety, and environmental friendliness. However, the charge‐storage mechanism involved remains a topic of controversy so far. Also, the practical energy density and cycling stability are still major issues for their applications. Herein, a free‐standing α‐MnO2 cathode for aqueous zinc‐ion batteries (ZIBs) is directly constructed with ultralong nanowires, leading to a rather high energy density of 384 mWh g?1 for the entire electrode. Greatly, the H+/Zn2+ coinsertion mechanism of α‐MnO2 cathode for aqueous ZIBs is confirmed by a combined analysis of in situ X‐ray diffractometry, ex situ transmission electron microscopy, and electrochemical methods. More interestingly, the Zn2+‐insertion is found to be less reversible than H+‐insertion in view of the dramatic capacity fading occurring in the Zn2+‐insertion step, which is further evidenced by the discovery of an irreversible ZnMn2O4 layer at the surface of α‐MnO2. Hence, the H+‐insertion process actually plays a crucial role in maintaining the cycling performance of the aqueous Zn/α‐MnO2 battery. This work is believed to provide an insight into the charge‐storage mechanism of α‐MnO2 in aqueous systems and paves the way for designing aqueous ZIBs with high energy density and long‐term cycling ability.  相似文献   

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N2 fixation is a challenging and rewarding issue. However, the traditional Haber–Bosch process consumes a large amount of fossil fuels, resulting in serious environmental pollution. Instead, N2 electroreduction is a promising way to convert and utilize N2. Among various N2 electroreduction methods, combining N2 reduction with batteries is simple and efficient. Here, a composite of ultrasmall Mo2C particles highly dispersed on N‐doped carbon nanosheets is prepared, and it is applied as the air cathode for Li–N2 batteries. Li–N2 batteries show high discharge capacity and superior reversibility, demonstrating that the Li–N2 battery is a promising platform for N2 electroreduction and electrochemical energy storage.  相似文献   

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