Developing highly efficient and low‐cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a ...nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble‐metal co‐catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so‐called L‐NiCo nanosheets with a nonstoichiometric composition and O2−/Co3+ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O2− and Co3+ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H2 evolution rate of 1.7 μmol h−1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.
A single‐phase photocatalyst, a hydrogen‐deficient nickel–cobalt double hydroxide, was generated by laser ablation. This photocatalyst can drive overall water splitting under solar light irradiation in the absence of sacrificial agents and noble metal co‐catalysts because of its unique composition and structure, with partially removed hydrogen atoms as well as O2− and Co3+ ions exposed on the surface.
A Au55 nanocluster with the composition of Au55(p‐MBT)24(Ph3P)6(SbF6)3 (p‐MBT=4‐methylbenzenethiolate) is synthesized via direct reduction of gold‐phosphine and gold‐thiolate precursors. ...Single‐crystal X‐ray diffraction reveals that this Au55 nanocluster features a face‐centered cubic (fcc) Au55 kernel, different from the well‐known two‐shell cuboctahedral arrangement in Au55(Ph3P)12Cl6. The Au55 cluster shows a wide optical absorption band with optical energy gap (Eg=1.28 eV). It is found that the exclusion of chloride is crucial for the formation of the title cluster, otherwise rod‐like Au25(SR)5(PPh3)10Cl22+ is obtained. The strategy to run synthetic reaction in the absence of halide leads to new members of phosphine/thiolate co‐protected metal nanoclusters. The Au55 nanocluster exhibits high catalytic activity and selectivity for electrochemical reduction of CO2 to CO; the Faradaic efficiency (FE) reaches 94.1 % at −0.6 V vs. reversible hydrogen electrode (RHE).
The gold nanocluster Au55(p‐MBT)24(Ph3P)6(SbF6)3 (p‐MBT=4‐methylbenzenethiolate) features a face‐centered cubic Au55 kernel. This cluster exhibits high catalytic activity and selectivity for electrochemical reduction of CO2 to CO, and the Faradaic efficiency (FE) reaches 94.1 % at −0.6 V. The exclusion of chloride is an effective strategy to generate new members of ligand‐protected metal nanoclusters.
High‐dielectric solvents were explored for enhancing the sulfur utilization in lithium–sulfur (Li−S) batteries, but their applications have been impeded by low stability at the lithium metal anode. ...Now a radical‐directed, lithium‐compatible, and strongly polysulfide‐solvating high‐dielectric electrolyte based on tetramethylurea is presented. Over 200 hours of cycling was realized in Li|Li symmetric cells, showing good compatibility of the tetramethylurea‐based electrolyte with lithium metal. The high solubility of short‐chain polysulfides, as well as the presence of active S3.− radicals, enabled pouch cells to deliver a discharge capacity of 1524 mAh g−1 and an energy density of 324 Wh kg−1. This finding suggests an alternative recipe to ether‐based electrolytes for Li−S batteries.
Li−S batteries: A lithium‐compatible and strongly polysulfide‐solvating high‐dielectric electrolyte based on tetramethylurea was proposed to direct a solvation‐mediated radical reaction pathway. It enables Li−S pouch cells to deliver an energy density of 324 Wh kg−1. Key: red=electrochemical, black=chemical, dashed=diffusion/precipitation.
The combination of one‐dimensional and two‐dimensional building blocks leads to the formation of hierarchical composites that can take full advantages of each kind of material, which is an effective ...way for the preparation of multifunctional materials with extraordinary properties. Among various building blocks, nanocarbons (e.g., carbon nanotubes and graphene) and layered double hydroxides (LDHs) are two of the most powerful materials that have been widely used in human life. This Feature Article presents a state‐of‐the‐art review of hierarchical nanocomposites derived from nanocarbons and LDHs. The properties of nanocarbons, LDHs, as well as the combined nanocomposites, are described first. Then, efficient and effective fabrication methods for the hierarchical nanocomposites, including the reassembly of nanocarbons and LDHs, formation of LDHs on nanocarbons, and formation of nanocarbons on LDHs, are presented. The as‐obtained nanocomposites derived form nanocarbons and LDHs exhibited excellent performance as multifunctional materials for their promising applications in energy storage, nanocomposites, catalysis, environmental protection, and drug delivery. The fabrication of LDH/carbon nanocomposites provides a novel method for the development of novel multifunctional nanocomposites based on the existing nanomaterials. However, knowledge of their assembly mechanism, robust and precise route for LDH/nanocarbon hybrid with well designed structure, and the relationship between structure, properties, and applications are still inadequate. A multidisciplinary approach from the scope of materials, physics, chemistry, engineering, and other application areas, is highly required for the development of this advanced functional composite materials.
Hierarchical nanocomposites derived from nanocarbons and layered double hydroxides, representing the latest frontier for arrangement and construction of different low‐dimensional nanomaterials as building blocks, are reviewed. The article highlights the fabrication of novel hierarchical nanoarchitectures via bottom‐up self‐organization and their promising applications in energy storage, materials science, catalysis, environmental protection, and drug delivery, with a focus on hot topics and future challenges in this field.
Lithium–sulfur (Li–S) batteries are deemed as future energy storage devices due to ultrahigh theoretical energy density. Cathodic polysulfide electrocatalysts have been widely investigated to promote ...sluggish sulfur redox kinetics. Probing the surface structure of electrocatalysts is vital to understanding the mechanism of polysulfide electrocatalysis. In this work, we for the first time identify surface gelation on disulfide electrocatalysts. Concretely, the Lewis acid sites on disulfides trigger the ring‐opening polymerization of the dioxolane solvent to generate a surface gel layer, covering disulfides and reducing the electrocatalytic activity. Accordingly, a Lewis base triethylamine (TEA) is introduced as a competitive inhibitor. Consequently, Li–S batteries with disulfide electrocatalysts and TEA afford high specific capacity and improved rate responses. This work affords new insights on the actual surface structure of electrocatalysts in Li–S batteries.
Surface gelation on disulfide electrocatalysts in Li–S batteries is identified for the first time. The gel layer, formed through the solvent polymerization triggered by the Lewis acid sites, covers the active electrocatalytic sites and renders reduced redox kinetics. Herein, a Lewis base triethylamine is introduced to suppress the surface gelation and promote the electrocatalytic activity of disulfide electrocatalysts.
Lithium (Li) metal has been considered a promising anode for next‐generation high‐energy‐density batteries. However, the low reversibility and intricate Li loss hinder the widespread implementation ...of Li metal batteries. Herein, we quantitatively differentiate the dynamic evolution of inactive Li, and decipher the fundamental interplay among dynamic Li loss, electrolyte chemistry, and the structure of the solid electrolyte interphase (SEI). The actual dominant form in inactive Li loss is practically determined by the relative growth rates of dead Li0 and SEI Li+ because of the persistent evolution of the Li metal interface during cycling. Distinct inactive Li evolution scenarios are disclosed by ingeniously tuning the inorganic anion‐derived SEI chemistry with a low amount of film‐forming additive. An optimal polymeric film enabler of 1,3‐dioxolane is demonstrated to derive a highly uniform multilayer SEI and decreased SEI Li+/dead Li0 growth rates, thus achieving enhanced Li cycling reversibility.
The fundamental interplay among Li dynamic loss behavior, electrolyte composition, and the structure of the solid electrolyte interphase (SEI) layer was quantitatively elucidated. The actual dominant form in inactive Li loss is determined by the relative growth rates of dead Li0 and SEI Li+ as the anode interface undergoes processive evolution during cycling. The mechanistic studies shed fresh light on the interfacial dynamics of the Li‐metal anode.
Exploring advanced strategies in alleviating the thermal runaway of lithium‐metal batteries (LMBs) is critically essential. Herein, a novel electrolyte system with thermoresponsive characteristics is ...designed to largely enhance the thermal safety of 1.0 Ah LMBs. Specifically, vinyl carbonate (VC) with azodiisobutyronitrile is introduced as a thermoresponsive solvent to boost the thermal stability of both the solid electrolyte interphase (SEI) and electrolyte. First, abundant poly(VC) is formed in SEI with thermoresponsive electrolyte, which is more thermally stable against lithium hexafluorophosphate compared to the inorganic components widely acquired in routine electrolyte. This increases the critical temperature for thermal safety (the beginning temperature of obvious self‐heating) from 71.5 to 137.4 °C. The remained VC solvents can be polymerized into poly(VC) as the battery temperature abnormally increases. The poly(VC) can not only afford as a barrier to prevent the direct contact between electrodes, but also immobilize the free liquid solvents, thereby reducing the exothermic reactions between electrodes and electrolytes. Consequently, the internal‐short‐circuit temperature and “ignition point” temperature (the starting temperature of thermal runaway) of LMBs are largely increased from 126.3 and 100.3 °C to 176.5 and 203.6 °C. This work provides novel insights for pursuing thermally stable LMBs with the addition of various thermoresponsive solvents in commercial electrolytes.
A thermoresponsive electrolyte is introduced into a working cell to relieve the exothermic reactions between electrodes and electrolytes, the internal short circuit. The critical temperature for thermal safety, “ignition point” of battery, and internal‐short‐circuit temperature of batteries with thermoresponsive electrolyte increase from 71.5, 100.3, and 126.3 °C to 137.4, 203.6, and 176.5 °C compared with routine electrolyte.
Columnar Lithium Metal Anodes Zhang, Xue‐Qiang; Chen, Xiang; Xu, Rui ...
Angewandte Chemie International Edition,
November 6, 2017, Letnik:
56, Številka:
45
Journal Article
Recenzirano
The rechargeable lithium metal anode is of utmost importance for high‐energy‐density batteries. Regulating the deposition/dissolution characteristics of Li metal is critical in both fundamental ...researches and practical applications. In contrast to gray Li deposits featured with dendritic and mossy morphologies, columnar and uniform Li is herein plated on lithium‐fluoride (LiF)‐protected copper (Cu) current collectors. The electrochemical properties strongly depended on the microscale morphologies of deposited Li, which were further embodied as macroscale colors. The as‐obtained ultrathin and columnar Li anodes contributed to stable cycling in working batteries with a dendrite‐free feature. This work deepens the fundamental understanding of the role of LiF in the nucleation/growth of Li and provides emerging approaches to stabilize rechargeable Li metal anodes.
Columnar Li deposition is obtained on uniform and dense nucleation sites formed by regulation of LiF. The obvious relation between microstructure and macroscale color provides an emerging descriptor to judge the uniformity of the deposited Li. Ultrathin and stable Li anodes are further developed to meet the intensive demand for high‐energy‐density batteries.
Lithium (Li) metal is regarded as a “Holy Grail” electrode for next‐generation high‐energy‐density batteries. However, the electrochemical behavior of the Li anode under a practical working state is ...poorly understood, leading to a gap in the design strategy and the aim of efficient Li anodes. The electrochemical diagram to reveal failure mechanisms of ultrathin Li in pouch cells is demonstrated. The working mode of the Li metal anode ranging from 1.0 mA cm−2/1.0 mAh cm−2 (28.0 mA/28.0 mAh) to 10.0 mA cm−2/10.0 mAh cm−2 (280.0 mA/280.0 mAh) is investigated and divided into three categories: polarization, transition, and short‐circuit zones. Powdering and the induced polarization are the main reasons for the failure of the Li electrode at small current density and capacity, while short‐circuit occurs with the damage of the separator leading to safety concerns being dominant at large current and capacity. The electrochemical diagram is attributed from the distinctive plating/stripping behaviors of Li metal, accompanied by dendrites thickening and/or lengthening, and heterogeneous distribution of dendrites. A clear understanding in the electrochemical diagram of ultrathin Li is the primary step to rationally design an effective Li electrode and render a Li metal battery with high energy density, long lifespan, and enhanced safety.
The failure mechanisms of ultrathin lithium in pouch cells can be divided into three categories: polarization, transition, and short‐circuit. A clear working pattern for ultrathin Li metal in pouch cells is established, which can potentially assist in designing a promising strategy for an advanced Li metal anodes.
Safe and high‐energy‐density rechargeable batteries are increasingly indispensable in the pursuit of a wireless and fossil‐free society. Advancements in present battery technologies and the ...investigation of next‐generation batteries highly depend on the ever‐deepening fundamental understanding and the rational designs of working electrodes, electrolytes, and interfaces. However, accurately analyzing energy materials and interfaces is severely hindered by their intrinsic limitations of air and electron‐beam sensitivity, which restrains the research of energy materials in a low‐efficiency trial‐and‐error paradigm. The emergence of cryogenic electron microscopy (cryo‐EM) has enabled the nondestructive characterization of air‐ and electron‐beam sensitive energy materials in the microscale and nanoscale, and even at atomic resolutions, affording closer insights into the primary chemistry and physics of working batteries. Herein, the development of cryo‐EM and the applications in detecting energy materials are reviewed and analyzed from its overwhelming advantages in disclosing the underlying mystery of energy materials. Critical sample preparation methods as the precondition for cryo‐EM are compared, which strongly affect the characterization accuracy. Furthermore, new developments in the analysis of energy materials, especially bulk electrodes and interfaces in lithium metal batteries, are presented according to different functions of cryo‐EM. Finally, future directions of cryo‐EM for analyzing energy materials are prospected.
Cryogenic electron microscopy is employed in analyzing energy materials. New insights into the relationship between the action of a battery and the electrode, electrolyte, and interface chemistries are presented. This affords new perspectives for battery studies and guides the rational design of energy materials for a sustainable society.
