The activity and accessibility of MoS2 edge sites are critical to deliver high hydrogen evolution reaction (HER) efficiency. Here, a porous carbon network confining ultrasmall N-doped MoS2 ...nanocrystals (N-MoS2/CN) is fabricated by a self-templating strategy, which realizes synergistically structural and electronic modulations of MoS2 edges. Experiments and density functional theory calculations demonstrate that the N dopants could activate MoS2 edges for HER, while the porous carbon network could deliver high accessibility of the active sites from N-MoS2 nanocrystals. Consequently, N-MoS2/CN possesses superior HER activity with an overpotential of 114 mV at 10 mA cm–2 and excellent stability over 10 h, delivering one of best MoS2-based HER electrocatalysts. Moreover, this study opens a new venue for optimizing materials with enhanced accessible catalytic sites for energy-related applications.
Smart integration of transition‐metal sulfides/oxides/nitrides with the conductive MXene to form hybrid materials is very promising in the development of high‐performance anodes for next‐generation ...Li‐ion batteries (LIBs) owing to their advantages of high specific capacity, favorable Li+ intercalation structure, and superior conductivity. Herein, a facile route was proposed to prepare strongly coupled MoS2 nanocrystal/Ti3C2 nanosheet hybrids through freeze‐drying combined with a subsequent thermal process. The Ti3C2 host could enhance the reaction kinetics and buffer the volume change of MoS2 at a low content (8.87 wt %). Thus, the MoS2/Ti3C2 hybrids could deliver high rate performance and excellent cycling durability. As such, high reversible capacities of 835.1 and 706.0 mAh g−1 could be maintained after 110 cycles at 0.5 A g−1 and 1390 cycles at 5 A g−1, respectively, as well as an outstanding rate capability with a capacity retention over 65.8 % at 5 A g−1. This synthetic strategy could be easily extended to synthesize other high‐performance MXene‐supported hybrid electrode materials.
Power couple: Strongly coupled MoS2 nanocrystal/Ti3C2 nanosheet hybrids with high MoS2 content deliver high lithium‐ion storage capacity, eminent rate capability, and excellent long‐term cycling durability.
Ni-rich layered LiNi 1−x−y Mn x Co y O 2 (NMC, x + y < 0.5) oxides have been demonstrated to be promising cathode materials for high-energy lithium-ion batteries. However, when cycled at high ...voltages, NMC cathode materials with high Ni content usually show unsatisfactory capacity decay and voltage fading due to side reactions and electrochemical irreversibility during prolonged lithiation/delithiation cycles. Here, we report a Mn-rich Li 0.65 Mn 0.59 Ni 0.12 Co 0.13 O δ (LMNCO) material that consists of layered Li 2 MnO 3 and spinel LiMn 1.5 Ni 0.5 O 4 -type components. LMNCO is a desirable shell material for improving the high-voltage cycling stability of Ni-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode materials. Core–shell-structured NMC811@ x % LMNCO materials were fabricated with satisfactory structural conformality via sonofragmentation followed by solvent evaporation-induced self-assembly and post-annealing processes. The optimized NMC811@5% LMNCO cathode material can deliver an initial discharge capacity of 150.0 mA h g −1 at 5C (1C = 200 mA g −1 ) in a voltage range of 2.7–4.6 V vs. Li + /Li with 83.4% retention for up to 500 cycles, significantly superior to that of the bare NMC811 material (75.6%). The Mn-rich shell also enables the effective stabilization of the Ni-rich cathode materials for long-term cycling at high voltages and 55 °C. In addition, this work offers a synthetic prototype for the fabrication of conformal core–shell-structures, which could be adopted for the surface modification of various functional materials to achieve enhanced performance in device applications.
Electrochemical performances of spinel cathode materials have been evaluated in a broad voltage range of 2.0–4.8 V vs. Li/Li+ via in-situ integrating a layered Li2MnO3 phase for high-voltage and ...high-capacity lithium ion batteries. Effects of sintering temperatures on manipulating hybrid spinel-layered structures have been systematically studied during the decomposition of nonstoichiometric Li0.65Mn0.59Ni0.12Co0.13Oδ material. The spinel component undergoes a phase transition from an initial Li4Mn5O12-type to a LiMn1.5Ni0.5O4-type spinel structure under high temperatures above 700 °C; meanwhile the content of layered Li2MnO3 component is increased. Li2MnO3-stabilized spinel-layered cathodes can deliver the discharge capacity more than 225 mA h/g at 0.1 C and exhibit outstanding capacity retentions above 90% at 0.5 C (1 C = 250 mA/g) in an extended voltage range between 2.0 and 4.8 V. In addition to clarify significant Li2MnO3 impacts on improving cycling stability of spinel cathode materials, it is noticeable that LiMn1.5Ni0.5O4-based spinel materials can effectively suppress the electrochemical activation of the layered Li2MnO3 up to 4.8 V. This work sheds lights on tailoring hybrid structures and maximizing electrochemical performances of Li2MnO3-based spinel-layered cathode materials for superior lithium ion batteries.
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•Integrated spinel-layered composite materials are synthesized.•Effects of heating temperature on tailoring spinel-layered structures are studied.•Incorporating a layered Li2MnO3 results in enhanced performances of spinel cathodes.•Spinel LiMn1.5Ni0.5O4 suppresses electrochemical activation of Li2MnO3 up to 4.8 V.•Li2MnO3-stabilized spinel cathode is promising for superior lithium ion batteries.
High‐performance and affordable electrocatalysts from earth‐abundant elements are desirably pursued for water splitting involving hydrogen evolution reaction (HER) and oxygen evolution reaction ...(OER). Here, a bifunctional electrocatalyst of highly crystalline Mo2C nanoparticles supported on carbon sheets (Mo2C/CS) was designed toward overall water splitting. Owing to the highly active catalytic nature of Mo2C nanoparticles, the high surface area of carbon sheets and efficient charge transfer in the strongly coupled composite, the designed catalysts show excellent bifunctional behavior with an onset potential of −60 mV for HER and an overpotential of 320 mV to achieve a current density of 10 mA cm−2 for OER in 1 m KOH while maintaining robust stability. Moreover, the electrolysis cell using the catalyst only requires a low cell voltage of 1.73 V to achieve a current density of 10 mA cm−2 and maintains the activity for more than 100 h when employing the Mo2C/CS catalyst as both anode and cathode electrodes. Such high performance makes Mo2C/CS a promising electrocatalyst for practical hydrogen production from water splitting.
One catalyst, two gases: Molybdenum carbide‐based materials (Mo2C/CS) with controllable structure and composition are synthesized. The optimal composite as a bifunctional electrocatalyst exhibits outstanding performance towards both hydrogen and oxygen evolution reactions in 1 m KOH. The alkali electrolyzer delivers a current density of 10 mA cm−2 at a low cell voltage of 1.73 V.
Although 2D Ti3C2Tx is a good candidate for supercapacitors, the restacking of nanosheets hinders the ion transport significantly at high scan rates, especially under practical mass loading (>10 mg ...cm−2) and thickness (tens of microns). Here, Ti3C2Tx‐NbN hybrid film is designed by self‐assembling Ti3C2Tx with 2D arrays of NbN nanocrystals. Working as an interlayer spacer of Ti3C2Tx, NbN facilitates the ion penetration through its 2D porous structure; even at extremely high scan rates. The hybrid film shows a thickness‐independent rate performance (almost the same rate capabilities from 2 to 20 000 mV s−1) for 3 and 50 µm thick electrodes. Even a 109 µm thick Ti3C2Tx‐NbN electrode shows a better rate performance than 25 µm thick pure Ti3C2Tx electrodes. This method may pave a way to controlling ion transport in electrodes composed of 2D conductive materials, which have potential applications in high‐rate energy storage and beyond.
A hybrid electrode of Ti3C2Tx flakes and 2D arrays of NbN nanocrystals shows a thickness‐independent rate performance (≈13% capacitance retention from 2 to 20 000 mV s−1) for 3 and 50 µm thick electrodes. The symmetric device assembled using two 50 µm Ti3C2Tx‐NbN‐0.5 hybrid films delivers an energy density of 23.1 Wh L−1 at a power density of 1.0 kW L−1.
Zinc (Zn) metal anodes suffer from the dendrite growth and hydrogen evolution reaction (HER) in classical aqueous electrolytes, which severely limit their lifespan. We propose a rational design of Ag ...x Zn y protective coatings with selective binding to Zn2+ against H+ to simultaneously regulate the Zn growth pattern and the HER kinetics. We further demonstrate that by tuning the composition of the Ag x Zn y coating the Zn deposition behavior can be readily tuned from the conventional plating/stripping (on Zn-AgZn3 coating) to alloying/dealloying (on Ag-AgZn coating), resulting in precise control of the Zn growth pattern. Moreover, the synergy of Ag and Zn further suppresses the competitive HER. As a result, the modified Zn anodes possess a significantly enhanced lifespan. This work provides a new strategy for enhancing the stability of Zn and potentially other metal anodes by precisely manipulating the binding strength of protons and metal charge carriers in aqueous batteries.
A high-voltage sodium-ion full battery has been assembled based on Na6Fe5(SO4)8 sulfate structurally integrated with 5 wt% carbon nanotubes (NFS@5%CNTs) acting as the cathode material, with ...commercialized hard carbon (HC) as the anode material. This full NFS@5%CNTs//HC cell delivers a practical working voltage of 3.6 V and an impressive energy density approaching 350 W h kg−1, and it can retain a specific capacity of 61.8 mA h g−1 after 1000 cycles at 2C. The superior sodium storage performance of this example of a full battery is attributed to the Na6Fe5(SO4)8 cathode material, which is structurally integrated with a conductive CNT component. The CNT additive is tightly implanted and runs through the whole NFS bulk, improving the electrochemical performance of NFS@x%CNTs cathode materials during the reversible intercalation/deintercalation of sodium ions. The optimized CNT content for NFS@x%CNTs cathode materials is evaluated to be 5 wt%, resulting in high initial capacities of 110.2 and 86.4 mA h g−1 at 0.1 and 2C, respectively. This work introduces a new derivative of sodium iron sulfates to act as a high-energy cathode material for sodium ion batteries, together with offering an effective CNT-assisted method for enhancing electrochemical performance. A full sodium-ion battery is further developed with a high working voltage and high energy/power densities for practical large-scale applications.
Potassium ion hybrid capacitors (KICs) have drawn tremendous attention for large-scale energy storage applications because of their high energy and power densities and the abundance of potassium ...sources. However, achieving KICs with high capacity and long lifespan remains challenging because the large size of potassium ions causes sluggish kinetics and fast structural pulverization of electrodes. Here, we report a composite anode of VO2–V2O5 nanoheterostructures captured by a 3D N-doped carbon network (VO2–V2O5/NC) that exhibits a reversible capacity of 252 mAh g–1 at 1 A g–1 over 1600 cycles and a rate performance with 108 mAh g–1 at 10 A g–1. Quantitative kinetics analyses demonstrate that such great rate capability and cyclability are enabled by the capacitive-dominated potassium storage mechanism in the interfacial engineered VO2–V2O5 nanoheterostructures. The further fabricated full KIC cell consisting of a VO2–V2O5/NC anode and an active carbon cathode delivers a high operating voltage window of 4.0 V and energy and power densities up to 154 Wh kg–1 and 10 000 W kg–1, respectively, surpassing most state-of-the-art KICs.
Zinc (Zn) metal anodes suffer from the dendrite growth and hydrogen evolution reaction (HER) in classical aqueous electrolytes, which severely limit their lifespan. We propose a rational design of Ag
...Zn
protective coatings with selective binding to Zn
against H
to simultaneously regulate the Zn growth pattern and the HER kinetics. We further demonstrate that by tuning the composition of the Ag
Zn
coating the Zn deposition behavior can be readily tuned from the conventional plating/stripping (on Zn-AgZn
coating) to alloying/dealloying (on Ag-AgZn coating), resulting in precise control of the Zn growth pattern. Moreover, the synergy of Ag and Zn further suppresses the competitive HER. As a result, the modified Zn anodes possess a significantly enhanced lifespan. This work provides a new strategy for enhancing the stability of Zn and potentially other metal anodes by precisely manipulating the binding strength of protons and metal charge carriers in aqueous batteries.
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