Showing papers in "Advanced Energy Materials in 2017"
TL;DR: In this paper, the authors highlight the recent progress in high-sulfur-loading Li-S batteries enabled by hierarchical design principles at multiscale, particularly, basic insights into the interfacial reactions, strategies for mesoscale assembly, unique architectures, and configurational innovation in the cathode, anode, and separator.
Abstract: Owing to high specific energy, low cost, and environmental friendliness, lithium–sulfur (Li–S) batteries hold great promise to meet the increasing demand for advanced energy storage beyond portable electronics, and to mitigate environmental problems. However, the application of Li–S batteries is challenged by several obstacles, including their short life and low sulfur utilization, which become more serious when sulfur loading is increased to the practically accepted level above 3–5 mg cm−2. More and more efforts have been made recently to overcome the barriers toward commercially viable Li–S batteries with a high sulfur loading. This review highlights the recent progress in high-sulfur-loading Li–S batteries enabled by hierarchical design principles at multiscale. Particularly, basic insights into the interfacial reactions, strategies for mesoscale assembly, unique architectures, and configurational innovation in the cathode, anode, and separator are under specific concerns. Hierarchy in the multiscale design is proposed to guide the future development of high-sulfur-loading Li–S batteries.
1,364 citations
TL;DR: In this article, the authors proposed the use of a typical family of TMDs with hexagonal system, which shows similar crystal structure to that of graphite lamellar with an interlayer spacing of 5.76 Å and showed that the interlayer space of VS2 can self adapt to the intercalation of Zn2+ with an expansion along the c-axis.
Abstract: DOI: 10.1002/aenm.201601920 class of materials show great potential for the insertion/extraction of multivalent ions (Zn2+, Mg2+, Al3+) owing to the characteristic of large layer spacing and high conductivity. Among all the TMDs, VS2 is a typical family member of TMDs with hexagonal system, which shows similar crystal structure to that of graphite lamellar with an interlayer spacing of 5.76 Å.[25,30] There is a vanadium layer between two sulfur layers to form a kind of sandwich structure. In VS2 crystal structure, each V atom is arranged around six S atoms and connected with S atoms with covalent bonds. The interlayer spacing of VS2 is so large that enables the convenient insertion/extraction of lithium ions (0.69 Å), sodium ions (1.02 Å), zinc ions (0.74 Å) or their solvation sheath in electrolyte. However, to the best of our knowledge, there is no report about VS2 as the electrode materials for ZIBs. Herein, the VS2 nanosheets are synthesized via a facile hydrothermal reaction (Supporting Information), which deliver a high capacity of 190.3 mA h g−1 at a current density of 0.05 A g−1 and exhibit long-term cyclic stability as the cathode for ZIBs. The electrochemical reaction mechanism of such VS2 electrodes is further investigated systematically through a series of measurements including ex situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), in situ Raman, ex situ transmission electron microscopy (TEM). A reversible insertion/extraction process can be observed from all aspects. Both the ex situ TEM and ex situ XRD results demonstrate that the interlayer space of VS2 can self adapt to the intercalation of Zn2+ with an expansion along the c-axis (only 1.73%) and a slightly shrink along the aand b-axes, which plays a key role in the realization of long-life ZIBs. All the above evidences reveal that the VS2 is a promising cathode material with high capacity and good cyclic stability for ZIBs. The crystal structure of the as-prepared VS2 is tested by XRD. All characteristic peaks are in accordance with the standard card of VS2 (JCPDS NO. 01-089-1640) (Figure 1a). The Raman spectrum of the VS2 in the range of 100–1100 cm−1 is shown in Figure 1b. Six peaks located at 140.4, 192.0, 282.0, 406.6, 687.8, and 993.2 cm−1 are observed, which correspond to the rocking and stretching vibrations of V–S bonds or their combination.[25] The morphology and microstructures of as-prepared VS2 are investigated by field emission scanning electron microscopy (SEM) and high-resolution TEM (HRTEM). As shown in Figure 1c, The VS2 flowers are assembled by nanosheets with a diameter of 5–8 μm and a thickness of 50–100 nm. The d-spacing calculated from selected area electron diffraction (SAED) patterns are 2.89 and 1.64 Å (Figure 2f), which match the d-spacing values of (002) and (110) crystal planes of VS2, respectively. TEM and corresponding HRTEM images in Figure 2e show VS2 nanosheets with a d-spacing of ≈5.76 Å, The continuous researches of energy-storage devices have gained considerable attention in our world which results from the increased development of new-type energy caused by energy crisis and environmental pollution.[1–3] In the past several decades, lithium ion batteries have been widely explored and applied to various fields as they deliver higher energy density compared to other secondary batteries.[4,5] Nevertheless, the processing cost, complicated issues of safety, the limited lithium resources as well as some environmental issues lead to an urgent challenge for exploring new energy storage system.[6,7] The rechargeable aqueous batteries, such as aqueous sodiumion batteries and aqueous Zn ion batteries (ZIBs) have received incremental attention because of cost effectiveness and material abundance.[8–16] There is interest in aqueous ZIBs due to the safety, low cost, abundance of Zn source, and utilizing divalent cations to increase charge-storage capabilities. However, existing aqueous ZIBs are far from achieving the goals of excellent performances demanded by the ever increasing energy consumption. It’s hard to find cathode materials suitable for the reversible intercalation/deintercalation of Zn ions (or their solvation sheath in electrolyte), which limits the developmen of ZIBs.[16] The previous explorations of the cathode material mostly focus on manganese dioxide (MnO2) and Prussian blue analogues, whereas, the former suffers a poor rate performance and a rapid capacity fading, while the latter delivers limited capacities (about 50 mA h g−1).[17–22] Recently, Nazar and co-workers reported a high-capacity and long-life aqueous rechargeable zinc battery, composing of a Zn0.25V2O5⋅nH2O nanobelts cathode, 1 m ZnSO4 electrolyte, and a zinc anode.[23] The work indicates that the layered structure materials show great potential for the cathode of ZIBs. During the past decades, layered transition-metal dichalcogenides (TMDs), such as MoS2, WS2, and VS2 have received significant attentions in a variety of fields for their outstanding characteristic (graphene-like layered structure, direct bandgap, and fast ion diffusion).[24–26] These properties make TMDs potential candidates for battery electrode materials. When applied as the electrode materials for lithium/sodium ion battery, some excellent studies have been reported.[27–29] Also, this
884 citations
TL;DR: In this article, the authors discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or transmitting excess solar energy (infrared radiation) in such a way that comfortable indoor temperatures can be maintained throughout the year.
Abstract: Windows are vital elements in the built environment that have a large impact on the energy consumption in indoor spaces, affecting heating and cooling and artificial lighting requirements. Moreover, they play an important role in sustaining human health and well-being. In this review, we discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or transmitting excess solar energy (infrared radiation) in such a way that comfortable indoor temperatures can be maintained throughout the year. Moreover, we place emphasis on windows that maintain transparency in the visible region so that additional energy is not required to retain natural illumination. We discuss a number of ways to fabricate windows which remain as permanent infrared control elements throughout the year as well as windows which can alter transmission properties in presence of external stimuli like electric fields, temperature and incident light intensity. We also show the potential impact of these windows on energy saving in different climate conditions.
877 citations
TL;DR: In this paper, the status of room-temperature potassium-ion batteries is reviewed in light of recent concerns regarding the rising cost of lithium and the fact that room temperature sodium ion batteries have yet to be commercialized thus far.
Abstract: The status of room-temperature potassium-ion batteries is reviewed in light of recent concerns regarding the rising cost of lithium and the fact that room-temperature sodium-ion batteries have yet to be commercialised thus far. Initial reports of potassium-ion cells appear promising given the infancy of the research area. This review presents not only an overview of the current potassium-ion battery literature, but also attempts to provide context by describing previous developments in lithium-ion and sodium-ion batteries and the electrochemical reaction mechanisms discovered thus far. Perspectives and directions on the techniques available to characterize newly developed battery materials are also provided based on our experience and knowledge from the literature. It is hoped that through this review, the potential of potassium-ion batteries as a competitive energy-storage technology will be realised, and the accessibility and available knowledge of the techniques required to develop the technology will be made apparent.
801 citations
TL;DR: In this paper, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized.
Abstract: The ever-increasing demand of lithium-ion batteries (LIBs) caused by the rapid development of various electronics and electric vehicles will be hindered by the limited lithium resource. Thus sodium-ion batteries (SIBs) have been considered as a promising potential alternative for LIBs owing to the abundant sodium resource and similar electrochemical performances. In recent years, significant achievements regarding anode materials which restricted the development of SIBs in the past decades have been attained. Significantly, the sodium storage feasibility of carbon materials with abundant resource, low cost, nontoxicity and high safety has been confirmed, and extensive investigation have demonstrated that the carbonaceous materials can become promising electrode candidates for SIBs. In this review, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized. Additionally, the critical issues, challenges and perspectives are provided to further understand the carbonaceous anode materials.
800 citations
TL;DR: In this article, a facile two-step solution method to rational design of a novel electrode of hollow NiCo2O4 nanowall arrays on flexible carbon cloth substrate is reported.
Abstract: Metal-organic frameworks (MOFs) are promising porous precursors for the construction of various functional materials for high-performance electrochemical energy storage and conversion. Herein, a facile two-step solution method to rational design of a novel electrode of hollow NiCo2O4 nanowall arrays on flexible carbon cloth substrate is reported. Uniform 2D cobalt-based wall-like MOFs are first synthesized via a solution reaction, and then the 2D solid nanowall arrays are converted into hollow and porous NiCo2O4 nanostructures through an ion-exchange and etching process with an additional annealing treatment. The as-obtained NiCo2O4 nanostructure arrays can provide rich reaction sites and short ion diffusion path. When evaluated as a flexible electrode material for supercapacitor, the as-fabricated NiCo2O4 nanowall electrode shows remarkable electrochemical performance with excellent rate capability and long cycle life. In addition, the hollow NiCo2O4 nanowall electrode exhibits promising electrocatalytic activity for oxygen evolution reaction. This work provides an example of rational design of hollow nanostructured metal oxide arrays with high electrochemical performance and mechanical flexibility, holding great potential for future flexible multifunctional electronic devices.
792 citations
TL;DR: In this article, the current state of our understanding of the OER mechanism on PEM-compatible heterogeneous electrocatalysts, before comparing and contrast that to the OOR mechanism on homogenous catalysts.
Abstract: The low efficiency of the electrocatalytic oxidation of water to O2 (oxygen evolution reaction-OER) is considered as one of the major roadblocks for the storage of electricity from renewable sources in form of molecular fuels like H2 or hydrocarbons Especially in acidic environments, compatible with the powerful proton exchange membrane (PEM), an earth-abundant OER catalyst that combines high activity and high stability is still unknown Current PEM-compatible OER catalysts still rely mostly on Ir and/or Ru as active components, which are both very scarce elements of the platinum group Hence, the Ir and/or Ru amount in OER catalysts has to be strictly minimized Unfortunately, the OER mechanism, which is the most powerful tool for OER catalyst optimization, still remains unclear In this review, we first summarize the current state of our understanding of the OER mechanism on PEM-compatible heterogeneous electrocatalysts, before we compare and contrast that to the OER mechanism on homogenous catalysts Thereafter, an overview over monometallic OER catalysts is provided to obtain insights into structure-function relations followed by a review of current material optimization concepts and support materials Moreover, missing links required to complete the mechanistic picture as well as the most promising material optimization concepts are pointed out
759 citations
TL;DR: In this paper, the synthesis of transition-metal (Fe, Co, Ni) based metal-organic frameworks and their derivatives with the focus on their application in supercapacitors and batteries is presented.
Abstract: Transition-metal (Fe, Co, Ni) based metal-organic framework materials with controllable structures, large surface areas and adjustable pore sizes have attracted wide research interest for use in next-generation electrochemical energy-storage devices. This review introduces the synthesis of transition-metal (Fe, Co, Ni) based metal-organic frameworks and their derivatives with the focus on their application in supercapacitors and batteries.
686 citations
TL;DR: In this article, a bimetal FeCo nanoparticles encapsulated in in situ grown nitrogen-doped graphitic carbon nanotubes with bamboo-like structure were used for oxygen reduction/evolution electrocatalysts.
Abstract: Rational design and exploration of robust and low-cost bifunctional oxygen reduction/evolution electrocatalysts are greatly desired for metal–air batteries. Herein, a novel high-performance oxygen electrode catalyst is developed based on bimetal FeCo nanoparticles encapsulated in in situ grown nitrogen-doped graphitic carbon nanotubes with bamboo-like structure. The obtained catalyst exhibits a positive half-wave potential of 0.92 V (vs the reversible hydrogen electrode, RHE) for oxygen reduction reaction, and a low operating potential of 1.73 V to achieve a 10 mA cm−2 current density for oxygen evolution reaction. The reversible oxygen electrode index is 0.81 V, surpassing that of most highly active bifunctional catalysts reported to date. By combining experimental and simulation studies, a strong synergetic coupling between FeCo alloy and N-doped carbon nanotubes is proposed in producing a favorable local coordination environment and electronic structure, which affords the pyridinic N-rich catalyst surface promoting the reversible oxygen reactions. Impressively, the assembled zinc–air batteries using liquid electrolytes and the all-solid-state batteries with the synthesized bifunctional catalyst as the air electrode demonstrate superior charging–discharging performance, long lifetime, and high flexibility, holding great potential in practical implementation of new-generation powerful rechargeable batteries with portable or even wearable characteristic.
670 citations
TL;DR: In this article, Li deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector, and an electrochemomechanical model of plating-induced Li infiltration is proposed.
Abstract: Li deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector. Four types of ion-conducting, inorganic solid electrolytes are tested: Amorphous 70/30 mol% Li2S-P2S5, polycrystalline β-Li3PS4, and polycrystalline and single-crystalline Li6La3ZrTaO12 garnet. The nature of lithium plating depends on the proximity of the current collector to defects such as surface cracks and on the current density. Lithium plating penetrates/infiltrates at defects, but only above a critical current density. Eventually, infiltration results in a short circuit between the current collector and the Li-source (anode). These results do not depend on the electrolytes shear modulus and are thus not consistent with the Monroe–Newman model for “dendrites.” The observations suggest that Li-plating in pre-existing flaws produces crack-tip stresses which drive crack propagation, and an electrochemomechanical model of plating-induced Li infiltration is proposed. Lithium short-circuits through solid electrolytes occurs through a fundamentally different process than through liquid electrolytes. The onset of Li infiltration depends on solid-state electrolyte surface morphology, in particular the defect size and density.
665 citations
TL;DR: In this paper, the authors focus on the challenges and recent progress in the development of Si anodes for lithium-ion battery, including initial Coulombic efficiency, areal capacity, and material cost, which call for more research effort and provide a bright prospect for the widespread applications of silicon anodes in the future lithium ion batteries.
Abstract: Silicon, because of its high specific capacity, is intensively pursued as one of the most promising anode material for next-generation lithium-ion batteries. In the past decade, various nanostructures are successfully demonstrated to address major challenges for reversible Si anodes related to pulverization and solid-electrolyte interphase. However, the electrochemical performance is still limited by challenges that stem from the use of nanomaterials. In this progress report, the focus is on the challenges and recent progress in the development of Si anodes for lithium-ion battery, including initial Coulombic efficiency, areal capacity, and material cost, which call for more research effort and provide a bright prospect for the widespread applications of silicon anodes in the future lithium-ion batteries.
TL;DR: In this article, small amounts of α-Fe2O3 nanosheets can actively promote exfoliation of g-C3N4, producing 2D hybrid that exhibits tight interfaces and an all-solid-state Z-scheme junction.
Abstract: Photocatalysis is the most promising method for achieving artificial photosynthesis, but a bottleneck is encountered in finding materials that could efficiently promote the water splitting reaction. The nontoxicity, low cost, and versatility of photocatalysts make them especially attractive for this application. This study demonstrates that small amounts of α-Fe2O3 nanosheets can actively promote exfoliation of g-C3N4, producing 2D hybrid that exhibits tight interfaces and an all-solid-state Z-scheme junction. These nanostructured hybrids present a high H2 evolution rate >3 × 104 µmol g-1 h-1 and external quantum efficiency of 44.35% at λ = 420 nm, the highest value so far reported among the family of g-C3N4 photocatalysts. Besides effectively suppressing the recombination of electron–hole pairs, this Z-scheme junction also exhibits activity toward overall water splitting without any sacrificial donor. The proposed synthetic route for controlled production of 2D g-C3N4-based structures provides a scalable alternative toward the development of highly efficient and active photocatalysts.
TL;DR: In this paper, a series of nanostructured hard carbon materials with controlled architectures is synthesized using a combination of in situ X-ray diffraction mapping, ex situ nuclear magnetic resonance (NMR), electron paramagnetic resonance, electrochemical techniques, and simulations.
Abstract: Hard carbon is one of the most promising anode materials for sodium-ion batteries, but the low Coulombic efficiency is still a key barrier. In this paper, a series of nanostructured hard carbon materials with controlled architectures is synthesized. Using a combination of in situ X-ray diffraction mapping, ex situ nuclear magnetic resonance (NMR), electron paramagnetic resonance, electrochemical techniques, and simulations, an “adsorption–intercalation” mechanism is established for Na ion storage. During the initial stages of Na insertion, Na ions adsorb on the defect sites of hard carbon with a wide adsorption energy distribution, producing a sloping voltage profile. In the second stage, Na ions intercalate into graphitic layers with suitable spacing to form NaC x compounds similar to the Li ion intercalation process in graphite, producing a flat low voltage plateau. The cation intercalation with a flat voltage plateau should be enhanced and the sloping region should be avoided. Guided by this knowledge, nonporous hard carbon material has been developed which has achieved high reversible capacity and Coulombic efficiency to fulfill practical application.
TL;DR: In this paper, the authors introduce the fundamentals of bifunctional ORR/OER electrocatalysis in rechargeable metal-air battery, a promising technology to meet the energy requirements for various applications.
Abstract: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the two most important reactions in rechargeable metal-air battery, a promising technology to meet the energy requirements for various applications. The development of low-cost, highly efficient and stable bifunctional ORR/OER catalysts is critical for a large-scale application of this technology. In this review, the authors first introduce the fundamentals of bifunctional ORR/OER electrocatalysis in alkaline electrolyte. Various types of nanostructured materials as bifunctional ORR/OER catalysts including metal oxide, hydroxide and sulfide, functional carbon material, metal, and their composites are then reviewed. The crucial factors that can be used to tune the activity of the catalyst towards ORR/OER are summarized, including (1) phase, morphology, crystal facet, defect, mixed-metal and strain engineering for metal oxide; (2) heteroatom doping, topological defects, and formation of metal-N-C structure for carbon material; (3) alloy effect for metal. These experiences lay the foundation for large scale application of metal-air battery and can also effectively guide the rational design of catalysts for other electrocatalytic reactions.
TL;DR: In this article, a method to significantly improve the gravimetric capacitance of Ti3C2Tx MXenes by cation intercalation and surface modification is reported, and the as-prepared electrodes show above 99% retention over 10 000 cycles.
Abstract: Supercapacitors attract great interest because of the increasing and urgent demand for environment-friendly high-power energy sources. Ti3C2, a member of MXene family, is a promising electrode material for supercapacitors owing to its excellent chemical and physical properties. However, the highest gravimetric capacitance of the MXene-based electrodes is still relatively low (245 F g−1) and the key challenge to improve this is to exploit more pseudocapacitance by increasing the active site concentration. Here, a method to significantly improve the gravimetric capacitance of Ti3C2Tx MXenes by cation intercalation and surface modification is reported. After K+ intercalation and terminal groups (OH−/F−) removing , the intercalation pseudocapacitance is three times higher than the pristine MXene, and MXene sheets exhibit a significant enhancement (about 211% of the origin) in the gravimetric capacitance (517 F g−1 at a discharge rate of 1 A g−1). Moreover, the as-prepared electrodes show above 99% retention over 10 000 cycles. This improved electrochemical performance is attributed to the large interlayer voids of Ti3C2 and lowest terminated surface group concentration. This study demonstrates a new strategy applicable to other MXenes (Ti2CTx, Nb2CTx, etc.) in maximizing their potential applications in energy storage.
TL;DR: In this paper, density function theory calculations reveal that nonelectroactive Zn behaves as an effective promoter for CoP-catalyzed hydrogen evolution reaction (HER) in both acidic and alkaline media.
Abstract: As a non-toxic species, Zn fulfills a multitude of biological roles, but its promoting effect on electrocatalysis has been rarely explored. Herein, the theoretic predications and experimental investigations that nonelectroactive Zn behaves as an effective promoter for CoP-catalyzed hydrogen evolution reaction (HER) in both acidic and alkaline media is reported. Density function theory calculations reveal that Zn doing leads to more thermal-neutral hydrogen adsorption free energy and thus enhanced HER activity for CoP catalyst. Electrochemical tests show that a Zn0.08Co0.92P nanowall array on titanium mesh (Zn0.08Co0.92P/TM) needs overpotentials of only 39 and 67 mV to drive a geometrical catalytic current of 10 mA cm-2 in 0.5 m H2SO4 and 1.0 m KOH, respectively. This Zn0.08Co0.92P/TM is also superior in activity over CoP/TM for urea oxidation reaction (UOR), driving 115 mA cm-2 at 0.6 V in 1.0 m KOH with 0.5 m urea. The high HER and UOR activity of this bifunctional electrode enables a Zn0.08Co0.92P/TM-based two-electrode electrolyzer for energy-saving hydrogen production, offering 10 mA cm-2 at a low voltage of 1.38 V with strong long-term electrochemical stability.
TL;DR: In this article, a novel bifunctional electrode consisting of two monolayer thick manganese dioxide (δ-MnO2) nanosheet arrays on a nickel foam, using a novel in-situ method was developed.
Abstract: Recently, defect engineering has been used to intruduce half-metallicity into selected semiconductors, thereby significantly enhancing their electrical conductivity and catalytic/electrocatalytic performance. Taking inspiration from this, we developed a novel bifunctional electrode consisting of two monolayer thick manganese dioxide (δ-MnO2) nanosheet arrays on a nickel foam, using a novel in-situ method. The bifunctional electrode exposes numerous active sites for electrocatalytic rections and displays excellent electrical conductivity, resulting in strong performance for both HER and OER. Based on detailed structure analysis and density functional theory (DFT) calculations, the remarkably OER and HER activity of the bifunctional electrode can be attributed to the ultrathin δ-MnO2 nanosheets containing abundant oxygen vacancies lead to the formation od Mn3+ active sites, which give rise to half-metallicity properties and strong H2O adsorption. This synthetic strategy introduced here represents a new method for the development of non-precious metal Mn-based electrocatalysts for eddicient energy conversion.
TL;DR: In this article, materials design strategies for constructing improved electrocatalysts based on MOF precursors/templates, with special emphasis on component manipulation, morphology control, and structure engineering, are presented.
Abstract: The key challenge to developing renewable and clean energy technologies lies in the rational design and synthesis of efficient and earth-abundant catalysts for a wide variety of electrochemical reactions. This review presents materials design strategies for constructing improved electrocatalysts based on MOF precursors/templates, with special emphasis on component manipulation, morphology control, and structure engineering. Guided by these strategies, recently developed MOF-derived materials have exhibited remarkable activity, selectivity, and stability for various energy-conversion processes, manifesting great potential for replacing precious-metal-based catalysts in next-generation energy devices. Existing challenges and opportunities regarding MOF-derived electrocatalysts are also discussed. It is anticipated that by extending current materials design strategies to a wider range of MOF precursors for various energy-related electrocatalytic reactions, significant advances toward achieving highly efficient electrocatalysts can be made.
TL;DR: In this paper, the metal sulfides (MSs) are used as anode material for NIBs and the corresponding electrochemical mechanisms are briefly discussed, with the hope of providing a fuller understanding of the associated electrochemical processes.
Abstract: The high demand for clean and renewable energy has fueled the exploration of advanced energy storage systems. As a potential alternative device for lithium ion batteries, sodium ion batteries (NIBs) have attracted extraordinary attention and are becoming a promising candidate for energy storage due to their low cost and high efficiency. Recent progress has demonstrated that metal sulfides (MSs) are very promising electrode candidates for efficient Na-storage devices, because of their excellent redox reversibility and relatively high capacity. In this review, recent developments of MSs as anode materials for NIBs are presented. The corresponding electrochemical mechanisms are briefly discussed. We also present critical issues, challenges, and perspectives with the hope of providing a fuller understanding of the associated electrochemical processes. Such an understanding is critical for tailoring and designing metal sulfides with the desired activity and stability.
TL;DR: In this paper, a 3D-networked, ultrathin, and porous Ni3S2/CoNi2S4 on Ni foam (NF) was successfully designed and synthesized by a simple sulfidation process from 3D Ni-Co precursors.
Abstract: 3D-networked, ultrathin, and porous Ni3S2/CoNi2S4 on Ni foam (NF) is successfully designed and synthesized by a simple sulfidation process from 3D Ni–Co precursors. Interestingly, the edge site-enriched Ni3S2/CoNi2S4/NF 3D-network is realized by the etching-like effect of S2− ions, which made the surfaces of Ni3S2/CoNi2S4/NF with a ridge-like feature. The intriguing structural/compositional/componental advantages endow 3D-networked-free-standing Ni3S2/CoNi2S4/NF electrodes better electrochemical performance with specific capacitance of 2435 F g−1 at a current density of 2 A g−1 and an excellent rate capability of 80% at 20 A g−1. The corresponding asymmetric supercapacitor achieves a high energy density of 40.0 W h kg−1 at an superhigh power density of 17.3 kW kg−1, excellent specific capacitance (175 F g−1 at 1A g−1), and electrochemical cycling stability (92.8% retention after 6000 cycles) with Ni3S2/CoNi2S4/NF as the positive electrode and activated carbon/NF as the negative electrode. Moreover, the temperature dependences of cyclic voltammetry curve polarization and specific capacitances are carefully investigated, and become more obvious and higher, respectively, with the increase of test temperature. These can be attributed to the components' synergetic effect assuring rich redox reactions, high conductivity as well as highly porous but robust architectures. This work provides a general, low-cost route to produce high performance electrode materials for portable supercapacitor applications on a large scale.
TL;DR: In this article, the authors present and discuss the development of carbon-based nanocomposite anodes in both Li ion batteries and Na ion batteries, focusing on strategies employed in fabricating such composites, with examples such as yolkshell structure, layered-by-layered structure, and composite comprising one or more carbon matrices.
Abstract: Carbon-oxide and carbon-sulfide nanocomposites have attracted tremendous interest as the anode materials for Li and Na ion batteries. Such composites are fascinating as they often show synergistic effect compared to their singular components. Carbon nanomaterials are often used as the matrix due to their high conductivity, tensile strength, and chemical stability under the battery condition. Metal oxides and sulfides are often used as active material fillers because of their large capacity. Numerous works have shown that by taking one step further into fabricating nanocomposites with rational structure design, much better performance can be achieved. The present review aims to present and discuss the development of carbon-based nanocomposite anodes in both Li ion batteries and Na ion batteries. The authors introduce the individual components in the composites, i.e., carbon matrices (e.g., carbon nanotube, graphene) and metal oxides/sulfides; followed by evaluating how advanced nanostructures benefit from the synergistic effect when put together. Particular attention is placed on strategies employed in fabricating such composites, with examples such as yolk–shell structure, layered-by-layered structure, and composite comprising one or more carbon matrices. Lastly, the authors conclude by highlighting challenges that still persist and their perspective on how to further develop the technologies.
TL;DR: Li et al. as mentioned in this paper used WS2 nanosheets as a composite electrode for Li-S batteries, which achieved a high rate capability (≈1501 and 450 mA h g−1 are achieved at charge/discharge rates of 0.1 C and 3 C, respectively).
Abstract: DOI: 10.1002/aenm.201601843 in order to restrict the loss of material. Furthermore, due to their scalability and flexibility, 3D flexible electronics (see Supporting Information (SI), where Table S1 contains a list) were considered revolutionary materials and were used in many fields such as imperceptible electronic devices, wearable electronic devices, and bionic technology.[11–13] Recently studies have shown the encapsulation of sulfur in the pores of carbon materials, such as meso-/microporous carbons,[11] cable-shaped carbon,[12] and carbon nanotubes/fibers,[13] can reduce the capacity fading. However, such nonpolar flexible carbon materials have a destructive disadvantage; they only have physical van der Waals (vdW) adsorption for polar Li2Sn, which leads to the facile detachment of Li2Sn from the carbon surface.[14] This proves that carbon-based materials alone cannot serve as the perfect host. In light of this new insight, various types of polar functional groups on carbon-based materials have been demonstrated to increase the interaction between Li2Sn species and the electrode; these materials can generally be categorized into three types: polymers (polyaniline, polypyrrole, poly(3,4ethylenedioxythiophene) (PEDOT)),[15] metal oxides (SiO2, TiO2, Al2O3, V2O5, MoO3), and transition-metal disulfides (TiS2, ZrS2,VS2). Zhang et al.[14] suggested that the moderate materials (such as TiS2, ZrS2, and VS2) are the best choices for battery electrodes. Recent research have revealed that the morphology of interconnected nanosheets, such as that found when MnO2 and MoS2 are vertically aligned on carbon materials, forms a 3D network producing electrodes with a stable cycling behavior.[13,17] Nevertheless, to obtain sophisticated pore structures and composites, tedious preparation methods were required for those materials, preventing them from having broad commercial applications. To further address the challenges and bring Li–S cells a step closer to commercialization, we obtained polar WS2 nanosheets deposited on carbon nanofibers (CNFs) using an efficient one-step hydrothermal reaction. Termed C@WS2, this is the first report of using this material as a composite electrode into Li–S batteries. In this flaky-structured C@WS2 composite electrode, dense WS2 nanosheets are wrapped around and anchored on the CNFs. Our experimental data was supported by a systematic simulation study, surveying WS2 with different binding strengths on Li2Sn species at different lithiation stages (n = 2, 3, 4, 6, 8). The nanoscale sulfur is firmly absorbed on the CNF surface not only through physical vdW forces, but also as a result of the WS2 polar functional groups. As a free-standing cathode material in Li–S batteries, the C@WS2 composite exhibits a high rate capability (≈1501 and 450 mA h g−1 are achieved at charge/discharge rates of 0.1 C and 3 C (1 C = 1675 mA h g−1), respectively) with outstanding Coulombic efficiencies (nearly 100%). The battery delivers Lithium–sulfur batteries, which exhibit a co-existence of high specific capacity (1675 mA h g−1) and energy density (2600 W h kg−1), have attracted increasing interest due to their low cost and environmentally friendly nature, both of which make them potentially applicable for electric vehicles (EVs) and large-scale stationary electric energy storage.[1,2] Unluckily, their implementation has been prevented by a series of reasons, including a weak cycle life and low capacities; these are caused by 1) the rapid dissolution of lithium polysulfide (Li2Sn) species into the electrolyte during the recharge, 2) the low electronic conductivity of both sulfur and lithium sulfide, and 3) the large volumetric expansion of sulfur (≈80%) upon lithiation.[3,4] Unquestionably, the poor performance of Li–S batteries is dominated by the issue of the soluble nature of the polysulfide (Sn) intermediates, which leads to their diffusion into the liquid electrolyte. This undesired phenomenon causes the mass transport of electroactive species, and it is termed the “polysulfide shuttle”.[4] To mitigate the detrimental effects of Sn solubility, over the past few decades, researchers have focused on two different aspects of the cell, following a logical train of thought. 1) For the electrolyte, some additives such as Li2S8 and LiNO3 have been added to slow down the polysulfide shuttle and improve Coulombic efficiency.[5] 2) In contrast, the majority of effort has been focused on the material used for the sulfur host; for example, conductive polymer matrices, such as polyaniline,[6] polypyrrole,[7] and poly(3,4-ethylenedioxythiophene),[8] have been shown to have a positive influence on increasing the cycle life of lithium–sulfur batteries. Although the above materials can relieve the effects of polysulfides shuttling, their ability to elongate the cell lifetime are yet far from perfect. To avoid corrosion on the current collector and reduce the production costs of the battery, aluminum was considered suitable for the current collector; it can be alternatively used in the place of Li–S electrodes. However, the role of a current collector can be for outstripping, transporting the current. Actually, 3D cathodes—such as sulfur–nickel foam (SNF)[9] and carbon nanotubes[10]—might be of interest for containing the active material and trapping the polysulfides during cycling,
TL;DR: In this article, a full aqueous Na-ion battery constructed on Na0.66[Mn0.34]O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses ( 0.006% per cycle) at a high rate (1 C).
Abstract: Narrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium-ion chemistry of practical energy density and cycle life. The sodium-ion water-in-salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na+-conducting solid-electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na-ion battery constructed on Na0.66[Mn0.66Ti0.34]O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li-ion and Na-ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin.
TL;DR: In this article, a controllable vacuum-diffusion method for gradual phosphidation of carbon coated metallic Co nanoparticles into Co/CoP Janus nanoparticles is reported, which exhibits excellent hydrogen evolution reaction and oxygen evolution reaction performance in various electrolytes across wide pH range along with high durability.
Abstract: A controllable vacuum-diffusion method for gradual phosphidation of carbon coated metallic Co nanoparticles into Co/CoP Janus nanoparticles is reported. Janus Co/CoP nanoparticles, as typical Mott–Schottky electrocatalysts, exhibit excellent hydrogen evolution reaction and oxygen evolution reaction performance in various electrolytes across wide pH range along with high durability. The Mott–Schottky Co/CoP catalyst can work as bifunctional electrode materials for overall water splitting in wide pH range and can achieve a current density of 10 mA cm−2 in neutral electrolyte at only 1.51 V.
TL;DR: Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4 as discussed by the authors.
Abstract: Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4%. The study shows the beneficial effect of Rb in improving the crystallinity and suppressing defect migration in the perovskite material. The light stability of the cells examined under continuous illumination of 12 h is improved upon the addition of Cs and Rb. After several cycles of 12 h light–dark, the cell retains 90% of its initial efficiency. In parallel, sputtered transparent conducting oxide thin films are developed to be used as both rear and front transparent contacts on quartz substrate with less than 5% parasitic absorption of near infrared wavelengths. Using these developments, semi-transparent perovskite cells are fabricated with steady state efficiency of up to 16.0% and excellent average transparency of ≈84% between 720 and 1100 nm. In a tandem configuration using a 23.9% silicon cell, 26.4% efficiency (10.4% from the silicon cell) in a mechanically stacked tandem configuration is demonstrated which is very close to the current record for a single junction silicon cell of 26.6%.
TL;DR: In this article, a Cu, Co-embedded nitrogen-enriched mesoporous carbon framework (CuCo@NC) is developed using, a facile Cu-confined thermal conversion strategy of zeolitic imidazolate frameworks (ZIF-67) pre-grown on Cu(OH)2 nanowires.
Abstract: Rational synthesis of hybrid, earth-abundant materials with efficient electrocatalytic functionalities are critical for sustainable energy applications. Copper is theoretically proposed to exhibit high reduction capability close to Pt, but its high diffusion behavior at elevated fabrication temperatures limits its homogeneous incorporation with carbon. Here, a Cu, Co-embedded nitrogen-enriched mesoporous carbon framework (CuCo@NC) is developed using, a facile Cu-confined thermal conversion strategy of zeolitic imidazolate frameworks (ZIF-67) pre-grown on Cu(OH)2 nanowires. Cu ions formed below 450 °C are homogeneously confined within the pores of ZIF-67 to avoid self-aggregation, while the existence of CuN bonds further increases the nitrogen content in carbon frameworks derived from ZIF-67 at higher pyrolysis temperatures. This CuCo@NC electrocatalyst provides abundant active sites, high nitrogen doping, strong synergetic coupling, and improved mass transfer, thus significantly boosting electrocatalytic performances in oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A high half-wave potential (0.884 V vs reversible hydrogen potential, RHE) and a large diffusion-limited current density are achieved for ORR, comparable to or exceeding the best reported earth-abundant ORR electrocatalysts. In addition, a low overpotential (145 mV vs RHE) at 10 mA cm−2 is demonstrated for HER, further suggesting its great potential as an efficient electrocatalyst for sustainable energy applications.
TL;DR: In this article, the fundamental operating mechanisms and challenges of Li intercalation in layered oxides, contrasts how these challenges play out differently for different materials (with emphasis on Ni-Co-Al and Ni-Mn-Co (NMC) alloys), and summarizes the extensive corpus of modifications and extensions to the layered lithium oxides.
Abstract: Although layered lithium oxides have become the cathode of choice for state-of-the-art Li-ion batteries, substantial gaps remain between the practical and theoretical energy densities. With the aim of supporting efforts to close this gap, this work reviews the fundamental operating mechanisms and challenges of Li intercalation in layered oxides, contrasts how these challenges play out differently for different materials (with emphasis on Ni–Co–Al (NCA) and Ni–Mn–Co (NMC) alloys), and summarizes the extensive corpus of modifications and extensions to the layered lithium oxides. Particular emphasis is given to the fundamental mechanisms behind the operation and degradation of layered intercalation electrode materials as well as novel modifications and extensions, including Na-ion and cation-disordered materials.
TL;DR: A broad overview of the field of photocatalysis can be found in this paper, where a detailed analysis of simple and integrated photocatalytic systems are presented. But the authors focus on the roles played by surface and interface chemical phenomena.
Abstract: Photocatalysis promises a solution to challenges associated with the intermittent nature of sunlight which is considered as renewable and ultimate energy source to power activities on Earth. This review aims to provide a broad overview of the field. Insight into natural photosynthesis is discussed first, which provides a scientific basis for most efforts on photocatalysis. Afterwards, the details of four existing types of photocatalysis are presented, namely photosynthesis by plants, photosynthesis by microalgae, photocatalysis by suspension and photoelectrocatalysis. Detailed analyses of simple photocatalysts and integrated photocatalytic systems are followed to shed light on the different functionalities of different components in a working photocatalyst. Special attention is given to the roles played by surface and interface chemical phenomena. Lastly, perspectives on artificial photosynthesis are discussed briefly at the end.
TL;DR: Inorganic-organic lead-halide perovskite solar cells have reached efficiencies above 22% within a few years of research as discussed by the authors, and achieved photovoltages of > 1.2 V for a material with a bandgap of 1.6 eV.
Abstract: Inorganic-organic lead-halide perovskite solar cells have reached efficiencies above 22% within a few years of research. Achieved photovoltages of >1.2 V are outstanding for a material with a bandgap of 1.6 eV - in particular considering that it is solution processed. Such values demand for low non-radiative recombination rates and come along with high luminescence yields when the solar cell is operated as a light emitting diode. This progress report summarizes the developments on material composition and device architecture, which allowed for such high photovoltages. It critically assesses the term "lifetime", the theories and experiments behind it, and the different recombination mechanisms present. It attempts to condense reported explanations for the extraordinary optoelectronic properties of the material. Amongst those are an outstanding defect tolerance due to antibonding valence states and the capability of bandgap tuning, which might make the dream of low-cost highly efficient solution-processed thin film solar cells come true. Beyond that, the presence of photon recycling will open new opportunities for photonic device design.