A Complexing Agent to Enable a Wide-Temperature Range Bromine-Based Flow Battery for Stationary Energy Storage

Bromine-based flow batteries (Br-FBs) are considered one of the most promising energy storage systems due to their features of high energy density and low cost. However, they generally suffer from uncontrolled diffusion of corrosive bromine particularly at high temperatures. That is because the interaction between polybromide anions and the commonly used complexing agent (N–methyl–N–ethyl–pyrrolidinium bromide [MEP]) decreases with increasing temperatures, which causes serious self-discharge and capacity fade. Herein, a novel bromine complexing agent, 1–ethyl–2–methyl–pyridinium bromide (BCA), is introduced in Br-FBs to solve the above problems. It is proven that BCA can combine with polybromide anions very well even at a high temperature of 60 °C. Moreover, the BCA contributes to decreasing the electrochemical polarization of Br⁻/Br₂ couple, which in turn improves their power density. As a result, a zinc–bromine flow battery with BCA as the complexing agent can achieve a high energy efficiency of 84% at 40 mA cm⁻², even at high temperature of 60 °C and it can stably run for more than 400 cycles without obvious performance decay. This paper provides an effective complexing agent to enable a wide temperature range Br-FB.     

Low-Cost Titanium–Bromine Flow Battery with Ultrahigh Cycle Stability for Grid-Scale Energy Storage

Flow batteries are one of the most promising large-scale energy-storage systems. However, the currently used flow batteries have low operation–cost-effectiveness and exhibit low energy density, which limits their commercialization. Herein, a titanium–bromine flow battery (TBFB) featuring very low operation cost and outstanding stability is reported. In this battery, a novel complexing agent, 3-chloro-2-hydroxypropyltrimethyl ammonium chloride, is employed to stabilize bromine/polybromides and suppress Br diffusion. The results reveal that the complexing agent effectively inhibits Br crossover and reduces Br-induced corrosivity, which in turn significantly improves the reliability of the TBFB system. The novel TBFB demonstrates 95% coulombic efficiency and 83% energy efficiency at 40 mA cm⁻² current density. Moreover, it can run smoothly for more than 1000 cycles without any capacity decay. Furthermore, an assembled 300 W TBFB stack can be continuously operated for more than 500 cycles, thereby confirming the practical applicability of the proposed TBFB. Because the TBFB utilizes an ultralow-cost electrolyte (41.29 $ kWh⁻¹) and porous polyolefin membranes, it serves as a reliable and low-cost energy-storage device. Therefore, considering its ultrahigh stability and low cost, the TBFB can be used as a large-scale energy-storage device.     

Fabrication of multi-filler thermoset-based composite bipolar plates for PEMFCs applications: Molding defects and properties characterizations

The bipolar plate (BP) material should possess contradictory properties. They should also manufacture from low-cost methods and materials. In the current investigation, thermoset-based composite materials reinforced with conductive fillers, and the compression molding process is implemented. In addition to fabricating the bipolar plates (BPs) with and without the flowing channels, alleviating the defects during the molding process is performed. The channels are perfectly formed on the plates with the designed depth of 0.65 mm and 0.5 mm of width. In the meanwhile, we alleviate different molding defects, which spoil the surface appearance and part properties. Regarding the physical properties, the water contact angle is measured to be around 85°. The through-plane electrical conductivity of molded plates showed high values up to 38 S/cm, and the interfacial contact resistance measured to be 18–24 mΩ cm². The mean value of the flexural strength of the produced samples was equal to 47 MPa, which is almost twice the DOE target (>25 MPa).     

Synergistic effect of aluminum hydroxide and expandable graphite on the flame retardancy of polyisocyanurate–polyurethane foams

For the first time, expandable graphite (EG) and aluminum hydroxide (ATH) was combined to improve the flame retardancy of polyisocyanurate–polyurethane (PIR–PUR) foam. The limited oxygen index increased from 26.5 for the PIR–PUR matrix to an incredible value of 92.8 when 24 phr (parts per 100 of matrix) EG and 60 phr ATH were incorporated into the matrix. Based on morphology observation and thermogravimetric analysis, it was speculated that two factors contributed to the improvement of flame retardancy primarily. First, ATH could effectively induce “villi” like particles, which was useful to form a dense char. The compact char layer could effectively impede the transport of bubbles and heat. Second, ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface of the composites. Thus, the degradation of the composite was slowed down and the diffusion of volatile combustible fragments to flame zone was delayed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39936.     

Reactive extrusion: A useful process to manufacture structurally modified PLA/o-MMT composites

In the present work, poly(lactic acid) (PLA) sheets reinforced with organically modified montmorillonite (o-MMT) were manufactured through reactive extrusion-calendering using a masterbatch approach in a pilot plant. Reaction monitoring analysis suggests the occurrence of premature reactions between o-MMT and the reactive agent; lowering further structural changes in the polymeric matrix. While calendered sheets exhibited a homogenous and preferential distribution of clay particles in MD, the coexistence of mixed structures, involving tactoids of various sizes as well as intercalated clay layers was observed. However, a higher and finer dispersion of o-MMT particles was achieved through clay–polymer tethering via chain extender molecules. Under tensile loading, the aforementioned clay dispersion enhanced multiple cavitation processes, notably improving PLA shear flow.     

Wood based PLA and PP composites: Effect of fibre type and matrix polymer on fibre morphology,dispersion and composite properties

This study presents a comparison of the effect of various wood fibre types in polylactic acid and polypropylene composites produced by melt processing. The study also reveals the reinforcing effect of pelletised wood fibres compared to conventionally used wood flour or refined fibres. Composites containing 30 wt.% of chemical pulps, thermomechanical pulp and wood flour were produced by compounding and injection moulding. Fibre morphologies were analysed before and after melt processing. The dispersion of the fibres and mechanical performance of the composites were also investigated. Fibre length was reduced during melt processing steps, reduction being higher with longer fibres. Wood fibres provided clearly higher plastic reinforcement than wood flour. Comparing the wood fibre types, TMP fibres provided the highest improvement in mechanical properties in polylactic acid composites with uniform fibre dispersion. In polypropylene composites, fibre selection is not as crucial.     

Design of functionally graded joints using a polyurethane-based adhesive with varying amounts of acrylate

Adhesives with graded properties along the bondline are being developed to increase the strength of adhesively bonded joints. Efforts to do this in the past have resulted in mixed results. Two adhesive parameters need to be considered: the geometry of the gradation and the material properties of the adhesive at different gradation levels. In order to consider both of these aspects, a computational model was created to aid in not only the design of adhesive gradations but also judge whether a specific adhesive gradation method will be able to result in strength increases. In this study, the model was introduced and compared with published results. A new adhesive gradation system was created by using a polyurethane-based adhesive with varying amounts of acrylate, and a numerical analysis was performed to determine the potential advantages of the adhesive gradation.     

EPR and Raman study of silicon layers obtained by gas detonation spraying

We demonstrate availability of gas detonation deposition spraying (GDS) to obtain silicon layers that can be used for production of solar cells. Silicon powder remaining as secondary raw material of silicon and/or silicon production is used during GDS. To study defects and structural perfection of initial powders and obtained layers, electron paramagnetic resonance (EPR) and Raman spectroscopy are used. It is shown that one part of EPR spectra displays resonances originating from different nearest-neighbor configurations of silicon dangling bonds, whereas an increase of the total number of paramagnetic defects in GDS silicon layer is related to the rise of conduction electrons or electrons filled band tail states. Thermal annealing of layers in hydrogen ambience further reduces the number of silicon dangling bonds owing to their passivation. Based on the results of X-ray diffraction, EPR and Raman spectroscopy it is assumed that the GDS Si layers are composed of randomly oriented and partially oxidized monocrystalline silicon grains. It is found that optical and photoelectric properties of the layers obtained indicate a possibility to apply them for solar cells production.     

Surface coating with poly(trifluoroethyl methacrylate) through rapid expansion of supercritical CO2 solutions

Rapid expansion of supercritical solutions (RESS) of poly(trifluoroethyl methacrylate), poly(TFEMA), was performed to produce ultrafine particles for spray coating application to improve the hydrophobicity of moisture-sensitive biodegradable materials. Carbon dioxide (CO₂) was used as the RESS solvent. Thermoplastic starch/poly(butylene adipate-co-terephthalate) (TPS/PBAT, 60:40 wt/wt) blend was used as the coating substrate. The objectives of this work were to determine the capacity of the RESS process for coating TPS-based material with poly(TFEMA), and to investigate the effect of RESS parameters – i.e. pre-expansion pressure and temperature (P_pre, T_pre) and poly(TFEMA) concentration – on the surface morphology and hydrophobicity of the coated materials. It was found that RESS produced poly(TFEMA) particles precipitated onto the surface of the TPS/PBAT substrate, with particle sizes ranging from 30 nm to several microns, depending on processing parameters. Rapid expansion of fluoropolymer solutions (0.3–1.0 wt%) with P_pre of 331 bar initiated from unsaturated conditions produced nanoparticles with a narrow size distribution of ∼30–70 nm; whereas larger particles with broader size distributions and a lower degree of agglomeration were obtained when supersaturated solutions were expanded with P_pre of 172 bar, especially at T_pre (80 °C) – higher than the glass transition temperature (73 °C) of poly(TFEMA). The surface coverage by the fluoropolymer increased with increasing P_pre and poly(TFEMA) concentration, but decreased with increasing T_pre. In addition, the hydrophobicity of the coated substrate, determined by water contact angle and water vapor transmission rate measurements, increased with increasing surface coverage.