Promising Cycling Stability Research Articles

Templated transformation of g-C3N4 nanosheets into nitrogen-doped hollow carbon sphere with tunable nitrogen-doping properties for application in Li-ions batteries

Fine control of nitrogen-doping in carbon materials is an urgent issue with great challenges for the applications in energy storage devices. In this work, nitrogen-doped hollow carbon spheres (NHCS) with tunable nitrogen-doping properties are synthesized by using graphitic carbon nitride (g-C3N4) nanosheets as precursor and Zinc powder as the template. A series of characterization techniques were performed to evidence the successful transformation of NHCS from g-C3N4. The nitrogen-doping level from 12.76 at.% to 27.82 at.% and the relative doping fractions of pyridinic-N, pyrrolic-N and graphitic-N for the g–C3N4–derived carbon materials can be easily tuned by controlling the synthetic temperatures. Serving as Li-ions battery anodes, the resultant NHCS delivers an acceptable initial discharge capacity of 1012.4 mAh g−1 under a current density of 0.1 A g−1 and a promising cycling stability (1064.5 mAh g−1 after 400 cycles) as well as an excellent rate performance (360 mAh g−1 at 10 A g−1). This work provides a facile gateway to synthesize high nitrogen-doped carbon materials applying to energy storage devices, from nitrogen-rich g-C3N4 precursor.

Flexible Conductive Cellulose Network-Based Composite Hydrogel for Multifunctional Supercapacitors.

With the continuous development of energy storage devices towards sustainability and versatility, the development of biomass-based multi-functional energy storage devices has become one of the important directions. In this study, a symmetric dual-function supercapacitor was constructed based on a cellulose network/polyacrylamide/polyaniline (CPP) composite hydrogel. The presented supercapacitor, with excellent electrochemical performance and an areal capacitance of 1.73 mF/cm2 at 5 mV/s, an energy density of 0.62 µW h/cm2 at a power density of 7.03 µW/cm2, a wide electrochemical window of 1.6 V and a promising cycling stability, can be achieved. The transmittance of the supercapacitor at 500 nm decreased by 9.6% after the electrification at 3 V, and the device can exhibit periodic transmittance change under the square potential input between 0.0 V and 3.0 V at regular intervals of 10 s. The present construction strategy provides a basis for the preparation of multifunctional devices with natural renewable materials and structures.

Construction of Cu-bridged Cu2O/MIL(Fe/Cu) catalyst with enhanced interfacial contact for the synergistic photo-Fenton degradation of thiacloprid

Cu2O/MIL(Fe/Cu) composite was fabricated via an in-situ Cu-bridging strategy to enhance interfacial synergistic effect of photo-Fenton catalysis for thiacloprid (TCL) degradation. Characterization results showed that: (1) Cu2O was proved to grow on the surface of MIL(Fe/Cu) in Cu2O/MIL(Fe/Cu) composite and display a high BET surface area of 1553 m2/g; (2) Cu2O/MIL(Fe/Cu) reduced band gap from 2.5 to 1.3 eV and extended absorption from UV to visible region; (3) Cu-bridge was proved to promote the intimate interface between Cu2O and MIL(Fe/Cu), which accelerated charge transferred and shortened the binding gap and the reaction pathway from photo-induced electrons to Fenton-generated radicals. As a result, this boosted the redox reaction of Fe2+/Fe3+ and promoted the reversible degree of this catalytic redox ability of MIL(Fe). Catalytic performance exhibited that (1) Cu2O/MIL(Fe/Cu) showed a fast kinetics (2–40 times faster than the state-of-the-art catalysts) and ultra-high mineralization (82.3% within 80 min) for TCL degradation; (2) Cu2O/MIL(Fe/Cu) showed a promising cycling stability due to improved charge transfer ability that could protect Cu2O from photo-corrosion during photo-Fenton reaction; (3) The catalytic performance of Cu2O/MIL(Fe/Cu) was characterized and seven photocatalytic intermediates were identified by both HPLC/MS and Surface Enhanced Raman Spectroscopy. The cyanoimino group in TCL was proved for the first time to be attacked primarily. Moreover, among all the detected intermediates, thiazolidin-2-amine (P6) was found to be the most stable intermediate to be degraded, and it can directly influence the TOC determination during photodegradation process.

Hollow sphere structured V2O3@C as an anode material for high capacity potassium-ion batteries

Carbon-coated V2O3 hollow spheres are synthesized by a solvothermal route, with promising cycling stability and rate performance for PIBs. The homogeneous carbon coating improves the electronic conductivity and the hollow structure buffers the volume change during cycling.

A visible-to-infrared broadband flexible electrochromic device based polyaniline for simultaneously variable optical and thermal management

A visible-to-infrared broadband flexible electrochromic device based on H2SO4-doped polyaniline films has been constructed for simultaneously variable optical and thermal management. Upon electrochemically manipulating, the demonstrated electrochromic device could change from a wide bandgap semiconductor to an insulator, causing the device to transform from a high thermal emitter with dark green to an optical reflector with bright yellow. High infrared emission changes of 0.4 and 0.3 for the device are observed at the wavelength ranges of 8–14 μm and 2.5–25 μm, respectively, which are higher than most reported electrochromic devices. A promising cycling stability and flexibility of the device are also observed. The thermal imaging results reveal that the device can be electrochemically and reversibly tuned to blend them with their environment. Furthermore, both the theoretical calculation and experimental results demonstrate that the device exhibits different heat transfer rates, facilitating the thermal management of the indoor object. The illustrated capabilities of the device make the electrochromic device highly promising for the optical management in visible-infrared regions and thermoregulation in indoor environment.

Brush-structured sulfur-polyaniline-graphene composite as cathodes for lithium-sulfur batteries

Abstract

Synthesis and research of layered CoS/graphene nanoflakes as sulfur cathode for high-energy lithium sulfur batteries

In this work, CoS nanoflakes were directly grown on graphene followed by sulfur storing by annealing sulfur/carbon disulfide and CoS nanoflakes at 155 °C for 10 h in N2. The microstructural and morphologies of the CoS/graphene nanoflake composites (CoS/G) were investigated by X-ray diffraction/photoelectron spectroscopy and electron microscopy. Benefiting from the strong chemical binds between CoS and lithium polysulfide species, and good electrical conductivity of graphene, the nanostructured sulfur cathode displays high sulfur utilization, promising rate capability and cycling stability compared to pristine sulfur cathode. The discharge capacity of the 100th cycle is maintained at 675.7 mA h g−1 at 0.5C.

Synthesis of Bi2O3-MnO2 Nanocomposite Electrode for Wide-Potential Window High Performance Supercapacitor

In this work, we report the synthesis of a Bi2O3-MnO2 nanocomposite as an electrochemical supercapacitor (ES) electrode via a simple, low-cost, eco-friendly, and low-temperature solid-state chemical process followed by air annealing. This as-synthesized nanocomposite was initially examined in terms of its structure, morphology, phase purity, and surface area using different analytical techniques and thereafter subjected to electrochemical measurements. Its electrochemical performance demonstrated excellent supercapacitive properties in a wide potential window. Its specific capacitance was able to reach 161 F g−1 at a current density of 1A g−1 and then showed a superior rate capability up to 10 A g−1. Furthermore, it demonstrated promising cycling stability at 5 A g−1 with 95% retention even after 10,000 charge–discharge cycles in a wide potential window of 1.3 V, evidencing the synergistic impact of both Bi2O3 and MnO2 in the Bi2O3-MnO2 ES electrode. Additionally, the practical reliability of the envisioned electrode was ascertained by the fabrication of a symmetric Bi2O3-MnO2//Bi2O3-MnO2 pencil-type supercapacitor device that displayed an energy density of 18.4 Wh kg−1 at a power density of 600 W kg−1 and a substantial cyclic stability up to 5000 cycles. Subsequently, an LED was also powered at its full brightness using three of these devices connected in series in order to demonstrate the real-time application of the Bi2O3-MnO2 ES electrode.

Three-dimensional self-doped hierarchical porous mussel nacre-derived carbons for high performance supercapacitors

A facile self-doping and self-templating strategy to prepare three-dimensional nitrogen-doped hierarchical porous carbons via direct carbonization of mussel nacre (MN) is developed. Self-templating can be effective to retain the origin structure and the volatile organic components can serve as carbon precursors for porous carbon. The typical MN-derived carbon (MNC) carbonized at 800 °C is endowed with high surface area of unique hierarchical porosity (consisting of macropores, mesopores and micropores), and high content of heteroatom functionalities (1.30 at.% N). Consequently, the performance in the alkaline KOH electrolyte system was particularly promising with the MNC-6 electrodes showing a high capacitance of 243.7 F g−1 at a current density of 1.0 A g−1 and a promising cycling stability with 85.7% capacitance retention at 1.0 A g−1 after 10,000 cycles. The present work provides a new avenue for facile and high efficient construction of N-doped hierarchical porous carbons for potential supercapacitor.

Structural engineering of SnS2/Graphene nanocomposite for high-performance K-ion battery anode

K-ion batteries (KIBs) are drawing increasing research interest as a promising supplement of Li-ion batteries due to the natural abundance of K resource. However, due to the large size of K+, high-capacity anodes are challenged by the structural stability of the active materials which are susceptible to large volumetric deformation after incorporating with a sufficient number of K+. Herein, using SnS2/graphene as an example, we demonstrated that high-performance KIBs anode could be achieved through collaborative efforts targeting on both the active material and the prepared electrode film. The electrochemically-active species of SnS2 were controlled into small nanoparticles with their size below 5 nm to provide sufficient reactive sites for K+ storage. Meanwhile, highly-resilient electrode film based on the prepared SnS2/graphene nanocomposite was built on aluminum (Al) current collector rather than the widely-used copper foil, forming a strong anode film with high peel strength to endure the potassiation/depotassiation process. In this way, the active species was able to deliver an extraordinary reversible capacity of 610 mAh g−1 with unprecedented high-rate capability (around 290 mAh g−1 at 2A g−1) and promising cycling stability. This contribution sheds light on the rational design of high-performance electrode for KIBs and beyond.

Hierarchical N/P-Co-Doped Porous Carbon as Host Materials for High-Performance Lithium Sulfur Battery

Lithium-sulfur battery (LSBs) is one of the most promising energy storage technologies due to its high energy density. The insulating properties of the sulfur and shuttle effect of the polysulfides during charge/discharge process limit its commercial application. In this work, we prepared a hierarchical N/P co-doped porous carbon (DPC) via NH4H2PO4 and KHCO3 dual-activation of the porous carbon, which was obtained by annealing of nano-calcium carbonate/sucrose composites. The resulting DPC/S composite as cathode materials for LSBs shows a promising long-term cycling stability (968.9 mAh g−1 after 100 cycles at 0.2 C) and rate performance (624.4 mAh g−1 at 1 C, 545.4 mAh g−1 at 2 C). The structural superiority of DPC host materials, i.e., highly porous structure, hierarchical pores and N/P co-doping contributes to the superior electrochemical performance of the materials. The simple synthesis process and low cost of the highly porous carbon makes it a promising candidate for encapsulation of active sulfur in lithium sulfur battery.

Li4Ti5O12: A Visible‐to‐Infrared Broadband Electrochromic Material for Optical and Thermal Management

AbstractBroadband electrochromism from visible to infrared wavelengths is attractive for applications like smart windows, thermal camouflage, and temperature control. In this work, the broadband electrochromic properties of Li4Ti5O12 (LTO) and its suitability for infrared camouflage and thermoregulation are investigated. Upon Li+ intercalation, LTO changes from a wide bandgap semiconductor to a metal, causing LTO nanoparticles on metal to transition from a super‐broadband optical reflector to a solar absorber and thermal emitter. Large tunabilities of 0.74, 0.68, and 0.30 are observed for the solar reflectance, mid‐wave infrared (MWIR) emittance, and long‐wave infrared (LWIR) emittance, respectively, with a tunability of 0.43 observed for a wavelength of 10 µm. The values exceed, or are comparable to notable performances in the literature. A promising cycling stability is also observed. MWIR and LWIR thermography reveal that the emittance of LTO‐based electrodes can be electrochemically tuned to conceal them amidst their environment. Moreover, under different sky conditions, LTO shows promising solar heating and subambient radiative cooling capabilities depending on the degree of lithiation and device design. The demonstrated capabilities of LTO make electrochromic devices based on LTO highly promising for infrared‐camouflage applications in the defense sector, and for thermoregulation in space and terrestrial environments.

Enabling High-Energy-Density Cathode for Lithium-Sulfur Batteries.

High-energy lithium-sulfur (Li-S) battery is built on high loading and dense sulfur electrodes. Unfortunately, these electrodes usually suffer from a low sulfur utilization rate and limited cycle life due to the gap in scientific knowledge between the fundamental research and the application at relevant scales. In this work, effects of electrode porosity on the electrode energy density, cell cycling stability, Li anode interface, and electrolyte/sulfur ratio were investigated on the basis of high-loading sulfur electrodes. Using electrodes with sulfur loading of 4 mg cm-2 and thickness at ∼60 μm, a high energy density of over 1300 Wh L-1 has been obtained at electrode level, which provides a decent basis for high-energy Li-S cell development. In addition, Li-S cells with the high-loading and dense electrodes demonstrate promising cycling stability (∼80% capacity retention for 200 cycles). These significant improvements are contributed by the synergistic effects of dense sulfur cathode, improved electrode wetting, and suppressed quick growth of the interphase layer on Li-metal anode. This study sheds light on rational design of sulfur cathode for balanced cell energy density and cycling life.

A New Approach to Synthesis Micrometer-Sized Porous Silicon Anode for Lithium Ion Batteries

A New Approach to Synthesis Micrometer-sized Porous Silicon Anode for Lithium Ion batteries Haiping Jia, Xiaolin Li, and Ji-Guang Zhang Pacific Northwest National Laboratory, Richland, WA, United States. With the increasing demand on high energy Li-ion batteries (LIBs) for electric vehicles and other large scale energy storage applications, silicon (Si) based composite material has been regarded as one of the most promising candidate to replace the state-of-the-art graphite anodes and can further boost the specific energy of LIBs to be more than 300 Wh/kg. Silicon has the highest practical capacity of 3,579 mAh g-1 and a relatively low lithiation potential of 0.2 V vs. Li/Li+. However, fast capacity fade still largely limits the practical application of Si based anode. A large volume change during lithiation and delithiation processes lead to pulverization and subsequent loss of electrical contact, continuous consumption of electrolyte, repeated breaking/formation of the solid electrolyte interphase (SEI) and an increase in the overall resistance. There has been significant effort to understand and mitigate the capacity fade in Si-based anodes exploiting nanostructured electrodes, surface coatings, additives and novel binders. These advances have paved the way for practical application of Si-based anodes for Li-ion battery applications. Although significant progress has been made, most nanostructured Si materials have to be prepared by high-cost processes (such as chemical vapor deposition) that are difficult to scale up. Therefore, there is an increasing need to prepare Si microparticles (SiMP) with high conductivity and stable structures. In this work, we developed a low-cost and scalable synthesis processes to make desired micronmeter scale SiO2/MWNT spheres. The highly spherical SiO2/MWNT macrobeads ranging from 500 nm to 10 µm in diameter were employed as template and silicon precursor (Figure 1a, b). The as-prepared material basically retains the original morphology of template and demonstrates unique hierarchical structure (Figure 1c, d). The fine primary silicon particles can shorten the Li+ transport route, and avoid the pulverization of SiMP. The obtained silicon composite delivers a reversible capacity of 1290 mAh g-1 at 1C and 87% capacity can be retained after 300 cycles. We attribute this promising cycling stability to the well-designed hierarchical structure, which provides: 1) enough void space to accommodate the volume change so that the swelling of the composite can be minimized; 2) good mechanical structure and electronic conductivity from the MWNT matrix. More details on the synthesis process and electrochemical performance of SiMP will be reported in this report. Figure 1. (a, b) SEM images of microsphere SiO2/MWNT; (c, d) SEM images of the obtained Si/MWNT. Figure 1

All-Fullerene-Based Cells for Nonaqueous Redox Flow Batteries.

Redox flow batteries have the potential to revolutionize our use of intermittent sustainable energy sources such as solar and wind power by storing the energy in liquid electrolytes. Our concept study utilizes a novel electrolyte system, exploiting derivatized fullerenes as both anolyte and catholyte species in a series of battery cells, including a symmetric, single species system which alleviates the common problem of membrane crossover. The prototype multielectron system, utilizing molecular based charge carriers, made from inexpensive, abundant, and sustainable materials, principally, C and Fe, demonstrates remarkable current and energy densities and promising long-term cycling stability.

A confined “microreactor” synthesis strategy to three dimensional nitrogen-doped graphene for high-performance sodium ion battery anodes

In virtue of abundant sodium resources, sodium ion batteries (SIBs) have been regarded as one of the most promising alternatives for large-scale energy storage applications. However, the absence of a suitable anode material makes it difficult to realize these applications. Here, we demonstrate an effective synthesis strategy of using a “microreactor” consisting of melamine fiber (inside) and graphene oxide (GO, outside) to fabricate three dimensional (3D) nitrogen doped (N-doped) graphene as high-performance anode materials for sodium ion batteries. Through a controlled pyrolysis, the inside melamine fiber and the outside GO layer has been converted into N-doped graphene and reduced graphene oxide (r-GO) respectively, and thus the “microreactor” is transformed into interconnected 3D N-doped graphene structures. Such highly desired 3D graphene structures show reversible sodium storage capacities up to ∼305 mA h g−1 after 500 cycles at a current density of 0.2 A g−1 and promising long cycling stability with a stable capacity of ∼198 mA h g−1 at 5 A g−1 after 5000 cycles. The high capacity and superior durability in combination with the facile synthesis procedure of the 3D graphene structure make it a promising anode material for SIBs and other energy storage applications.

Advanced anode for sodium-ion battery with promising long cycling stability achieved by tuning phosphorus-carbon nanostructures

Phosphorus is considered as a promising anode for Na-ion battery because of its high theoretical capacity of 2595mAhg−1. In this study, two phosphorus-carbon (P-C) composites with well-controlled compositions and nanostructures of P and C have been developed: P@YP composite with P confined within porous structure of YP-80F carbon and P@CNT with unconfined P deposited on the surface of carbon nanotube. The structure and electrochemical performance of these two composites have been studied to illustrate the effect of nanostructures of both C and P. P@YP composite with appropriate amount of P confined in nanopores can accommodate its large volume change upon sodiation/desodiation and enable a stable solid-electrolyte interphase (SEI), ensuring an excellent long-term cycling stability with superior capacity retention of 92% after 100 cycles and 46% after 1000 cycles. In contrast, the P@CNT composite with unconfined P nanostructures shows a rapid capacity decay with capacity retention of ~ 40.6% after 100 cycles, most likely due to unstable SEI during cycling, caused by the large volume changes of unconfined P in the P@CNT composite. The well-designed nanostructured P-C composite with P confined within porous structure of carbon is demonstrated to greatly enhance the electrochemical performance, leading to promising long-term cycling stability.

Tiny Particles with Big Impacts on Clean Future Energy

Tiny Particles with Big Impacts on Clean Future Energy

Perylene-Based All-Organic Redox Battery with Excellent Cycling Stability.

Organic materials derived from biomass can constitute a viable option as replacements for inorganic materials in lithium-ion battery electrodes owing to their low production costs, recyclability, and structural diversity. Among them, conjugated carbonyls have become the most promising type of organic electrode material as they present high theoretical capacity, fast reaction kinetics, and quasi-infinite structural diversity. In this letter, we report a new perylene-based all-organic redox battery comprising two aromatic conjugated carbonyl electrode materials, the prelithiated tetra-lithium perylene-3,4,9,10-tetracarboxylate (PTCLi6) as negative electrode material and the poly(N-n-hexyl-3,4,9,10-perylene tetracarboxylic)imide (PTCI) as positive electrode material. The resulting battery shows promising long-term cycling stability up to 200 cycles. In view of the enhanced cycling performances, the two organic materials studied herein are proposed as suitable candidates for the development of new all-organic lithium-ion batteries.

Nanostructured Li2Se cathodes for high performance lithium-selenium batteries

We report on a simple and fast route to prepare lithium selenide (Li2Se) nanoparticles and show a versatile solution-based method to form uniform nanostructured carbon (C)-Li2Se composites with and without additional carbon shell. We systematically compare electrochemical performance characteristics of 50–100nm high purity Li2Se nanoparticles with that of the C-Li2Se nanocomposites for rechargeable Li battery applications. While Li2Se nanopowder show high initial capacity, it suffers from active material loss and shuttle of dissolved polyselenides, resulting in low cycling stability and resistance growth, additionally aggravated by mechanical cathode degradation induced by repetitive volume changes during cycling. By embedding Li2Se nanoparticles into a conductive carbon matrix, mechanical stability of electrodes was greatly enhanced. More importantly, the dissolution and shuttle of polyselenides was suppressed significantly even for smaller (~20nm) and thus more reactive Li2Se nanoparticles. As a result, C-Li2Se nanocomposite cathodes showed high rate capability and promising cycling stability with carbon-shell protected C-Li2Se showing virtually no degradation in 100 cycles. When compared with somewhat similar lithium sulfide (Li2S) nanoparticles and C-Li2S electrodes, we observe lower over-potential at different C-rates in case of Li2Se and C-Li2Se materials, which is advantageous for battery applications. Based on the postmortem analysis, significant Li dendrite growth observed in Li2Se/Li cells did not take place in C-Li2Se/Li and C-Li2Se@C/Li cells, suggesting that polyselenide shuttle may affect Li plating morphology. Beyond the organic electrolyte-based Li-Se batteries, all-solid Li-Se batteries based on the produced C-Li2Se nanocomposite cathode were built for the first time using conventional Li2S-P2S5 solid state electrolyte. These solid state cells showed very promising cycling stability, a single flat plateau and very small voltage hysteresis in the range of 0.1–0.4V when tested at 60 and 80°C.