12 Search Results

We report the lithium–sulfur (Li–S) battery is one of the most promising battery systems due to its high theoretical energy density and low cost. Despite impressive progress in its development, there has been a lack of comprehensive analyses of key performance parameters affecting the energy density of Li–S batteries. Here, we analyse the potential causes of energy loss during battery operations. We identify two key descriptors (R_weight and R_energy) that represent the mass- and energy-level compromise of the full-cell energy density, respectively. A formulation for energy density calculations is proposed based on critical parameters, including sulfur mass loading, sulfur massmore » ratio, electrolyte/sulfur ratio and negative-to-positive electrode material ratio. The current progress of Ah-level Li–S batteries is also summarized and analysed. Finally, future research directions, targets and prospects for designing practical high-performance Li–S batteries are proposed.« less

Abstract All‐solid‐state batteries (ASSBs) show great potential as high‐energy and high‐power energy‐storage devices but their attainable energy/power density at room temperature is severely reduced because of the sluggish kinetics of lithium‐ion transport. Here a thermally modulated current collector (TMCC) is reported, which can rapidly cold‐start ASSBs from room temperature to operating temperatures (70–90 °C) in less than 1 min, and simultaneously enhance the transient peak power density by 15‐fold compared to one without heating. This TMCC is prepared by integrating a uniform, ultrathin (≈200 nm) nickel layer as a thermal modulator within an ultralight polymer‐based current collector. By isolating the thermal modulatormore » from the ion/electron pathway of ASSBs, it can provide fast, stable heat control yet does not interfere with regular battery operation. Moreover, this ultrathin (13.2 µm) TMCC effectively shortens the heat‐transfer pathway, minimizes heat losses, and mitigates the formation of local hot spots. The simulated heating energy consumption can be as low as ≈3.94% of the total battery energy. This TMCC design with good tunability opens new frontiers toward smart energy‐storage devices in the future from the current collector perspective.« less

Recently, alloys have been widely utilized as protection layers for homogenized Li growth. However, the protective mechanisms for different alloys are not clearly understood. In this work, guided by the binary phase diagrams, Mg, Au, Zn, Al, Fe, and Cu protective layers have been selected for study of their protective abilities and mechanisms. The selected metals can be classified into three categories according to the nature of their associated alloy protective layers: (1) metals with high solubility in Li while not forming any intermediate line compounds, e.g., Mg, which is good for fast Li stripping; (2) metals with limited solidmore » solubility but forming stable line compounds with Li upon the lithiation, e.g., Au, Zn, and Al, where the formed stable line compounds Li_xAu, Li_xZn, and Li_xAl will hamper Li kinetics; (3) metals with negligible mutual solubility and no line compound formation with Li, e.g., Fe and Cu, which block the Li stripping path and therefore result in the highest polarization voltage.« less

In lithium-sulfur (Li-S) chemistry, the electrically/ionically insulating nature of sulfur and Li2S leads to sluggish electron/ion transfer kinetics for sulfur species conversion. Sulfur and Li2S are recognized as solid at room temperature, and solid-liquid phase transitions are the limiting steps in Li-S batteries. Here, we visualize the distinct sulfur growth behaviors on Al, carbon, Ni current collectors and demonstrate that (i) liquid sulfur generated on Ni provides higher reversible capacity, faster kinetics, and better cycling life compared to solid sulfur; and (ii) Ni facilitates the phase transition (e.g., Li2S decomposition). Accordingly, light-weight, 3D Ni-based current collector is designed to controlmore » the deposition and catalytic conversion of sulfur species toward high-performance Li-S batteries. This work provides insights on the critical role of the current collector in determining the physical state of sulfur and elucidates the correlation between sulfur state and battery performance, which will advance electrode designs in high-energy Li-S batteries.« less

Nanomaterials provide many desirable properties for electrochemicalenergy storage devices due to their nanoscale size effect, which could be significantlydifferent from bulk or micron-sized materials. Particularly, confined dimensions playimportant roles in determining the properties of nanomaterials, such as the kinetics ofion diffusion, the magnitude of strain/stress, and the utilization of active materials.Nanowires, as one of the representative one-dimensional nanomaterials, have greatcapability for realizing a variety of applications in thefields of energy storage since theycould maintain electron transport along the long axis and have a confinement effectacross the diameter. In this review, we give a systematic overview of the state-of-the-artresearch progress onmore » nanowires for electrochemical energy storage, from rational designand synthesis,in situstructural characterizations, to several important applications inenergy storage including lithium-ion batteries, lithium-sulfur batteries, sodium-ionbatteries, and supercapacitors. The problems and limitations in electrochemical energystorage and the advantages in utilizing nanowires to address the issues and improve thedevice performance are pointed out. At the end, we also discuss the challenges and demonstrate the prospective for the futuredevelopment of advanced nanowire-based energy storage devices.« less

Lithium–sulfur (Li–S) batteries are enticing next-generation energy storage technologies due to their high theoretical energy density, environmental friendliness, and low cost. Yet, low conductivity of sulfur species, dissolution of polysulfides, poor conversion from sulfur reduction, and lithium sulfide (Li₂S) oxidation reactions during discharge–charge processes hinder their practical applications. Herein, under the guidance of density functional theory calculations, we have successfully synthesized large-scale single atom vanadium catalysts seeded on graphene to achieve high sulfur content (80 wt % sulfur), fast kinetic (a capacity of 645 mAh g^–1 at 3 C rate), and long-life Li–S batteries. Both forward (sulfur reduction) and reversemore » reactions (Li₂S oxidation) are significantly improved by the single atom catalysts. This finding is confirmed by experimental results and consistent with theoretical calculations. The ability of single metal atoms to effectively trap the dissolved lithium polysulfides (LiPSs) and catalytically convert the LiPSs/Li₂S during cycling significantly improved sulfur utilization, rate capability, and cycling life. Our work demonstrates an efficient design pathway for single atom catalysts and offers solutions for the development of high energy/power density Li–S batteries.« less

Lithium–sulfur batteries are promising for low-cost and high-energy storage, but their applications are still limited by poor cycling stability owing to soluble lithium polysulfide shuttling during battery operation. Avoiding shuttle effect is challenging but it is essential to avoid active material loss and prevent performance decay. We use an ultrathin layer of MoS₂ with thickness of 10–40 nm, which is 1–2 orders of magnitude thinner than conventional interlayers, for Li–S batteries to mitigate polysulfide shuttling. The MoS2 layer formed by exfoliated nanoflakes is deposited by the scalable liquid-based self-assembly method. With less than 1% of additional weight in the cathode,more » the MoS₂ interlayer with complete coverage inhibits polysulfide diffusion across the separator and therefore remarkably improves the battery performances. Reversible specific capacity reaches 1010 and 600 mA h g^–1 at 0.5 and 2C rates, respectively, which decay slowly over 400 cycles (0.11% per cycle). Moreover, the MoS₂ films with high density of catalytic active flake edges enable high areal sulfur loading up to 10 mg cm^–2 and areal capacity up to 9.7 mA h cm^–2 at a current density of 3.2 mA cm^–2.« less

With the increasing strategies aimed at repressing shuttle problems in the lithium–sulfur battery, dissolved contents of polysulfides are significantly reduced. Except for solid-state Li₂S₂ and Li₂S, aggregated phases of polysulfides remain unexplored, especially in well confined cathode material systems. Here, we report a series of nanosize polysulfide clusters and solid phases from an atomic perspective. The calculated phase diagram and formation energy evolution process demonstrate their stabilities and cohesive tendency. It is interesting to find that Li₂S₆ can stay in the solid state and contains short S₃ chains, further leading to the unique stability and dense structure. Simulated electronic propertiesmore » indicate reduced band gaps when polysulfides are aggregated, especially for solid phase Li₂S₆ with a band gap as low as 0.47 eV. In conclusion, their dissolution behavior and conversion process are also investigated, which provides a more realistic model and gives further suggestions on the future design of the lithium–sulfur battery.« less

A variety of methods including tuning chemical compositions, structures, crystallinity, defects and strain, and electrochemical intercalation have been demonstrated to enhance the catalytic activity. However, none of these tuning methods provide direct dynamical control during catalytic reactions. Here we propose a new method to tune the activity of catalysts through solid-state ion gating manipulation and adjustment (SIGMA) using a catalysis transistor. SIGMA can electrostatically dope the surface of catalysts with a high electron concentration over 5 × 10¹³ cm^–2 and thus modulate both the chemical potential of the reaction intermediates and their electrical conductivity. The hydrogen evolution reaction (HER) onmore » both pristine and defective MoS₂ were investigated as model reactions. Furthermore, our theoretical and experimental results show that the overpotential at 10 mA/cm² and Tafel slope can be in situ, continuously, dynamically, and reversibly tuned over 100 mV and around 100 mV/dec, respectively.« less

Dust filtration is a crucial process for industrial waste gas treatment. Great efforts have been devoted to improve the performance of dust filtration filters both in industrial and fundamental research. Conventional air-filtering materials are limited by three key issues: (1) Low filtration efficiency, especially for particulate matter (PM) below 1 μm; (2) large air pressure drops across the filter, which require a high energy input to overcome; and (3) safety hazards such as dust explosions and fires. Here, we have developed a “smart” multifunctional material which can capture PM with high efficiency and an extremely low pressure drop, while possessingmore » a flame retardant design. This multifunctionality is achieved through a core–shell nanofiber design with the polar polymer Nylon-6 as the shell and the flame retardant triphenyl phosphate (TPP) as the core. At 80% optical transmittance, the multifunctional materials showed capture efficiency of 99.00% for PM_2.5 and >99.50% for PM_10–2.5, with a pressure drop of only 0.25 kPa (0.2% of atmospheric pressure) at a flow rate of 0.5 m s^–1. Furthermore, during direct ignition tests, the multifunctional materials showed extraordinary flame retardation; the self-extinguishing time of the filtrate-contaminated filter is nearly instantaneous (0 s/g) compared to 150 s/g for unmodified Nylon-6.« less