Hydrogen storage in the iron series of porous Prussian blue analogues

The hydrogen storage has been studied in several series of porous Prussian blue analogues but not in the iron one, T₃[Fe(CN)₆]₂ with T = Mn, Co, Ni, Cu, Zn, Cd. In this contribution the study of the H₂ adsorption in that series of porous solids is discussed. For comparison, the H₂ adsorption isotherm in Fe₄[Fe(CN)₆]₃ was also recorded. All the samples to be studied were characterized from energy-dispersed spectroscopy, X-ray diffraction, infrared, Mössbauer, and thermogravimetric data. The cavity volume to be occupied by the hydrogen molecule was estimated from the amount of water molecules found within the cavity. The obtained value for the cavity volume was then used to calculate the density for the hydrogen storage within the cavity. The obtained density values remain below the value corresponding to its liquid state (71 g/L).     

Multi-metal doped high capacity and stable Prussian blue analogue for sodium ion batteries

Prussian blue analogues (PBA) are attractive positive electrode for sodium ion batteries due to their large interstitial sites and three-dimensional porous framework. However, they often suffer from irreversible phase transition upon charging and discharging, leading to fast capacity decay. In consideration that redox couples of Co²⁺/Co³⁺, Ni²⁺/Ni³⁺ and Fe²⁺/Fe³⁺ guarantee high capacity (~150 mA h g⁻¹), and Cu serves as a pillar to hold the PBA framework, here we synthesized a series of Cu, Co and Ni co-doped PBA, displaying high capacity and stable cycling performance with >98% capacity retention after 50 cycles.     

Modeling and simulation of 2D lithium‐ion solid state battery

The goal of the work presented here was to develop a simulation approach for studying the effects of materials and geometry on the performance of Li‐ion Solid State Batteries (SSB). Simulation provides the opportunity to explore, with ease, different material properties and cell geometries to optimize a Li‐ion SSB's performance. Simulations shown in this paper are time‐dependent and consider electrochemical reaction, heat transfer, the diffusion of Li‐ions and electrons in the electrolyte, and solid Li diffusion in the positive electrode. A 2D model was simulated and the results shown. The simulations were able to show discharge curves, heat flux, the concentration of Li‐ions, electrons, and solid Li at any time in the discharge cycle. Copyright © 2015 John Wiley & Sons, Ltd.     

All-solid-state electrochromic device based on poly(butyl viologen), Prussian blue, and succinonitrile

A new complementary electrochromic device (ECD) is described; it is based on poly(butyl viologen) (PBV) and Prussian blue (PB) confined to the electrode surfaces. PBV is a cathodically colored organic polymer, while PB is an anodically colored inorganic material. The two electrochromic materials were individually characterized in a 0.5 M KCl aqueous solution. On the basis of their properties, a PBV–PB ECD containing a solid-state electrolyte prepared by adding lithium tetrafluoroborate (LiBF₄) as a salt to succinonitrile (SN) was investigated. This all-solid-state ECD system showed good optical contrast with a coloration efficiency of ca. 163 cm²/C at 650 nm and good stability during 4000 cycles. The transmittance of the ECD at 650 nm changed from 73% (bleached) to 8% (darkened), with an applied potential of 1.7 V (−1.0 to 0.7 V) across the two electrodes. After 4000 cycles, the transmittance attenuation (ΔT) of the device was still at 86% of its original value, i.e. the ΔT value had decreased from 65% to 56%.     

Preparation of graphite carbon/Prussian blue analogue/palladium (GC/PBA/pd) synergistic-effect electrocatalyst with high activity for ethanol oxidation reaction

In this paper, newly graphite carbon/Prussian blue analogue/palladium (GC/PBA/Pd) synergistic-effect electrocatalyst for ethanol oxidation reaction were developed, with Co-based PBA (Co₃[Co(CN)₆]₂) as a co-catalyst. Structural analysis shows that the Co₃(Co(CN)₆)₂ nanoparticles were highly dispersed and inlaid on surface of GC nanosheets with outstanding structural stability. The GC/Co₃(Co(CN)₆)₂/Pd electrocatalyst exhibits significantly enhanced electrocatalytic activity towards ethanol oxidation with a maximum mass activity of 2644 A g^?1 Pd GC/Pd, which is more than double that of GC/Pd electrocatalyst (1249 A g^?1). Excellent electrochemical stability is also demonstrated for this GC/Co₃(Co(CN)₆)₂/Pd electrocatalyst. The enhanced electrocatalytic activity can be attributed to the synergistic effects of GC support and Co₃(Co(CN)₆)₂ promoter on the Pd electrocatalysts, in which Co₃(Co(CN)₆)₂ acts as a co-catalyst and GC acts as a conductive support.     

Cycling and at-rest stabilities of a complementary electrochromic device containing poly(3,4-ethylenedioxythiophene) and Prussian blue

PEDOT-based electrochromic devices (ECDs) have been investigated intensively in recent years. In order to obtain an ECD having long cycle life, the counter electrode and electrolyte used should be compatible in the electrochemical environment. Prussian blue (PB) is proven to be electrochemically stable when cycling in non-aqueous solutions. Thus a new organic-inorganic complementary ECD was assembled in combination with a PMMA-based gel polymer electrolyte. This ECD exhibited deep blue-violet when applying −2.1 V and became light blue when applying 0.6 V. Under these conditions, the transmittance of the ECD at 590 nm changed from 13.8% (−2.1 V) to 60.5% (+0.6 V) with a coloration efficiency of 338 cm²/C. The cell retained 55% of its maximum transmittance window (ΔT_max) after 50,640 repeated cycles. Moreover, the at-rest stability test revealed a transmittance window (ΔT) decay of 9.6% over a period of 107 days. Therefore, the proposed PEDOT-PB ECD may have potential for practical applications.     

Composite electrodes of disordered carbon and graphite for improved battery state estimation with minimal performance penalty

Voltage based state of charge (SOC) estimation is challenging for lithium ion batteries that exhibit little open circuit voltage (OCV) change over a large SOC range. We demonstrate that by using a composite negative electrode composed of disordered carbon and graphite, we were able to introduce additional features to the OCV-SOC relationship that facilitate voltage-based SOC estimation. In contrast to graphite, the potential of disordered carbon is sensitive to the state of charge; this behavior, when manifested in a lithium ion battery, gives rise to additional beneficial features of the cell OCV-SOC relationship in terms of state estimation. We have demonstrated the effectiveness of the approach by comparing model simulations and corresponding experimental data of a cell composed of LiFePO₄ positives and graphite + disordered carbon composite negative electrodes. Last, we find that although the graphite material has a higher coulombic capacity, very little (dynamic) performance loss is manifest with the mixed graphite + disordered carbon composite is employed.     

High‐performance solid PEO/PPC/LLTO‐nanowires polymer composite electrolyte for solid‐state lithium battery

Solid polymer composite electrolyte (SPCE) with good safety, easy processability, and high ionic conductivity was a promising solution to achieve the development of advanced solid‐state lithium battery. Herein, through electrospinning and subsequent calcination, the Li_0.33La_0.557TiO₃ nanowires (LLTO‐NWs) with high ionic conductivity were synthesized. They were utilized to prepare polymer composite electrolytes which were composed of poly (ethylene oxide) (PEO), poly (propylene carbonate) (PPC), lithium bis (fluorosulfonyl)imide (LiTFSI), and LLTO‐NWs. Their structures, thermal properties, ionic conductivities, ion transference number, electrochemical stability window, as well as their compatibility with lithium metal, were studied. The results displayed that the maximum ionic conductivities of SPCE containing 8 wt.% LLTO‐NWs were 5.66 × 10^?5 S cm^?1 and 4.72 × 10^?4 S cm^?1 at room temperature and 60°C, respectively. The solid‐state LiFePO₄/Li cells assembled with this novel SPCE exhibited an initial reversible discharge capacity of 135 mAh g^?1 and good cycling stability at a charge/discharge current density of 0.5 C at 60°C.     

Investigations on physicochemical properties and electrochemical performance of graphite felt and carbon felt for iron-chromium redox flow battery

In this paper, polyacrylonitrile-based graphite felt (GF), carbon felt (CF) and the effect of thermal activation on them with or without the catalyst (BiCl₃) are comprehensively investigated for iron-chromium redox flow battery (ICRFB) application. The physical-chemical parameters of GF and CF after the thermal activation is affected significantly by their graphitization degree, oxygen functional groups, and surface area. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results manifest that GF and CF before and after the thermal activation have different electrocatalytic activities owing to oxygen functional groups number increase and the graphitization degree decrease. In terms of the capacity decay rate, as oxygen functional groups provide shorter electrocatalytic pathways than bismuth ions, the performance of GF and CF after the thermal activation is more ideal. As a result, GF before and after the thermal activation exhibits higher efficiency (EE: 86%) and better stability at a charge-discharge current density of 60 mA·cm⁻² than those of CF during charge-discharge cycling, as the dominant limitation in an ICRFB is ohmic and activation polarization. Therefore, GF after thermal activation together with the addition of BiCl₃ in the electrolyte is a more promising electrode material for ICRFBs application than CF.     

A novel organic/inorganic composite solid electrolyte with functionalized layers for improved room‐temperature rate performance of solid‐state lithium battery

High ionic conductivity at room temperature (RT) and good ion transport capability at electrode/electrolyte interface are fundamental requirements for high‐rate solid‐state lithium batteries (SSBs). In this work, we designed a poly (propylene carbonate) (PPC)‐based organic/inorganic composite solid electrolyte (CSE) membrane with high filling of tantalum‐doped lithium lanthanum zirconium oxide (LLZTO) and functionalized layers for enhancing the RT rate performance of SSB. The synergistic effect of LLZTO and interfacial functionalized layers endows the NCM622/CSE/Li battery with high‐rate and cycling performances at RT. The SSB with 20% LLZTO‐filled solid electrolyte shows the initial capacities of 162.0, 148.5 and 130.1 mAh g^?1 at 1C, 2C, and 3C respectively, with retention capacities of 115.6, 104, and 100.6 mAh g^?1 after 150 cycles. This strategy for an organic/inorganic CSE is of great practical significance for the development of high‐rate SSBs.     

Ionanofluid plasticized electrolyte with improved electrical and electrochemical properties for high-performance lithium polymer battery

Herein, the electrochemical characteristics of Li/LiFePO₄ battery, comprising a new class of poly (ethylene oxide) (PEO) hosted polymer electrolytes, are reported. The electrolytes were prepared using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) dopant salt and imidazolium ionic liquid-based nanofluid (ionanofluid) as the plasticizer. Morphological, thermophysical, electrical, and electrochemical properties of these newly developed electrolytes were studied. Using FT-IR spectroscopy, the interactions between dopant salt plasticizers and the host polymer, within the electrolytes, were evaluated. The optimized 30 wt% ionanofluid plasticized electrolyte exhibits a room temperature ionic conductivity of 6.33 × 10⁻³ S cm⁻¹, wide electrochemical voltage window (~4.94 V vs Li/Li⁺) along with a moderately high value of lithium-ion transference number (0.47). The values are substantially higher than that of similar wt% IL plasticized electrolyte (7.85 × 10⁻⁴ S cm⁻¹, ~4.44 V vs Li/Li⁺ and ~ 0.28, respectively). Finally, the Li/LiFePO₄ battery, comprising optimized 30 wt% ionanofluid plasticized electrolyte, delivers 156 mAh g⁻¹ discharge capacity at 0.1 C rate and able to retain its 92% value after 50 cycles. Such a superior battery performance as compared to the IL plasticized electrolyte cell (137 mAh g⁻¹ and 84% after 50 cycles at the same current rate) would endow this ionanofluid a very promising plasticizer to develop electrolytes for next-generation lithium polymer battery.     

New lithium salts with croconato-complexes of boron for lithium battery electrolytes

A new lithium salt containing C₅O₅²⁻, lithium bis[croconato]borate (LBCB), and its novel derivative, lithium [croconato salicylato]borate (LCSB) were synthesized and characterized. The thermal characteristics of them and lithium bis[salicylato(2-)]-borate (LBSB) were examined by thermogravimetric analysis (TG). The thermal decomposition in Ar begins at 250, 328, and 350 °C for LBCB, LCSB, and LBSB, respectively. The order of the stability toward oxidation of these organoborates is LBCB > LCSB > LBSB, which differs from the thermal stability. The cyclic voltammetry study shows that the LiBCB and LCSB solutions in PC are stable up to 5.5 and 4.8 V versus Li⁺/Li, respectively. They are moderately soluble in common organic solvents, being 0.14, 0.16, and 1.4 mol dm⁻³ at 20 °C in EC + DME (molar ratio 1:1) for LBCB, LCSB, and LBSB, respectively. Ionic dissociation properties of LBCB and its derivatives were examined by conductivity measurements in PC, PC + DME, EC + DME, PC + THF, EC + THF (molar ratio 1:1) solutions. The conductivity values of the 0.10 mol dm⁻³ LBCB electrolyte in PC, PC + DME, EC + DME, PC + THF, EC + THF solutions are higher than those of LCSB and LBSB electrolytes. It means that LBCB has the higher dissociation ability in those solutions.     

LBDOB, a new lithium salt with benzenediolato and oxalato complexes of boron for lithium battery electrolytes

A new unsymmetrical lithium salt containing C₆H₄O₂²⁻[dianion of 1,2-benzenediol] and C₂O₄²⁻[dianion of oxalic acid], lithium [1,2-benzenediolato(2-)-O,O′ oxalato]borate (LBDOB), is synthesized and characterized. The thermal characteristics of it, lithium bis[1,2-benzenediolato(2-)-O,O′]borate (LBBB) and lithium bis(oxalate)borate (LiBOB) are examined by thermogravimetric (TG) analysis. The thermal decomposition in Ar begins at 250, 256, and 302 °C for LBBB, LBDOB, and LBOB, respectively. The order of the stability toward oxidation of these organoborates is LBOB > LBDOB > LBBB, which is in the same order of the thermal stability. The cyclic voltammetry study shows that the LBDOB solution in PC is stable up to 3.7 V vs. Li⁺/Li. They are soluble in common organic solvents. Ionic dissociation properties of LBDOB and its derivatives are examined by conductivity measurements in PC, PC + DME, EC + DME, PC + THF, EC + THF (molar ratio 1:1) solutions. The conductivity values of the 0.10 mold m⁻³ LBDOB electrolyte in PC, PC + DME, EC + DME, PC + THF, EC + THF solutions are higher than those of LBBB, but lower than those of LBOB electrolytes.     

A novel titania nanorods‐filled composite solid electrolyte with improved room temperature performance for solid‐state Li‐ion battery

Solid‐state batteries (SSBs) with room temperature (RT) performances had been one of the most promising technologies for energy storage. To achieve a chemical stable and high ionic conductive solid electrolyte, herein, a titania (TiO₂) (B) nanorods‐filled poly(propylene carbonate) (PPC)‐based organic/inorganic composite solid electrolyte (CSE) was prepared for the first time. It was found that by using TiO₂(B) nanorods, the ionic conductivity of the CSE membrane could be improved to 1.52 × 10^?4 S/cm, the electrochemical stable window was more than 4.6 V, and the tensile strength reaches 27 MPa with a strain less than 6%. The CSE was applied for SSB and showed excellent room temperature electrochemical performances. At 25°C, the LiFePO₄/CSE/Li SSB with 3%TiO₂‐filled CSE had the first cycle specific discharge capacity of 162 mAh/g with a capacity retention of 93% after 100 cycles at 0.3C. While the NCM622/CSE/Li SSB with 3%TiO₂‐filled CSE had the first specific discharge capacity of 165 mAh/g with a capacity retention of 88% after 100 cycles at 0.3C. The enhancement effect of TiO₂(B) nanorods could be ascribed that the rod‐like fillers provide more continuous Li‐ion transport path compared with nano particles, and the surface porosity and composition of TiO₂(B) nanorods could also improve the interfacial contact and Lewis acid‐base reaction sites between polymer and fillers. The TiO₂(B) nanorods‐filled CSE with high chemical stability, potential window, and ionic conductivity was promising to meet the requirements of SSBs.     

Fabrication and electrochemical performance of thin-film solid oxide fuel cells with large area nanostructured membranes

Thin-film solid oxide fuel cells (SOFCs) with large (5-mm square) membranes and ultra-thin La_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (LSCF) cathodes have been fabricated and their electrochemical performance was measured up to 500 °C. A grid of plated nickel on the cathode with 5–10 μm linewidth and 25–50 μm pitch successfully supported a roughly 200-nm-thick LSCF/yttria-stabilized zirconia/platinum membrane while covering less than 20% of the membrane area. This geometry yielded a maximum performance of 1 mW cm⁻² and 200 mV open-circuit voltage at 500 °C. Another approach toward realizing large area fuel cell junctions consists of depositing the membrane on a smooth substrate, covering it with a high-porosity material formed in situ, then removing the substrate. We have used a composite of silica aerogel and carbon fiber as the support, and show that this material can be created in flow channels etched into the underside of a silicon chip bonded to the top of the SOFC membrane. We anticipate these integrated fuel cell devices and structures to be of relevance to advancing low-temperature SOFCs for portable applications.     

An active balancer with rapid bidirectional charge shuttling and adaptive equalization current control for lithium-ion battery strings

This article proposes an active balancer, which features bidirectional charge shuttling and adaptive equalization current control, to fast counterbalance the state of charge (SOC) of cells in a lithium-ion battery (LIB) string. The power circuit consists of certain bidirectional buck-boost converters to transfer energy among the different cells back and forth. Owing to the characterization of the open-circuit voltage (OCV) vs SOC in LIB being relatively smooth near the SOC middle range, the SOC-inspected balance strategy can achieve more precise and efficient equilibrium than the voltage-based control. Accordingly, a compensated OCV-based SOC estimation is put forward to take into account the discrepancy of SOC estimation. Besides, the varied-duty-cycle (VDC) and curve-fitting modulation (CFM) methods are devised herein to tackle the problems of slow equalization rate and low balance efficacy, which arise from the diminution in balancing current as the SOC difference between the cells decreases in the later duration of equalization especially. The proposed strategies have taken the battery nonlinear characteristic and circuit parameter nonideality into account and can adaptively modulate the duty cycle with the SOC difference to keep balancing current constant throughout the balancing cycle. Simulated and experimental results are given to demonstrate the feasibility and effectiveness of the same prototype constructed. Compared with the fixed duty cycle and the VDC methods, the proposed CFM has the best balancing efficiency of 81.4%, and the balance time is shortened by 27.1% and 18.6%, respectively.     

Synthesis and characterization of nickel oxide/cobalt oxide nanocomposite for effective degradation of methylene blue and their comparative electrochemical study as electrode material for supercapacitor application

In this paper, we have synthesized a nanocomposite of nickel oxide (NiO) and cobalt oxide (Co₃O₄) using l-ascorbic acid which is named A(NC). Herein, A stands for l-ascorbic acid, N stands for nickel oxide (NiO), and C stands for cobalt oxide (Co₃O₄). Where l-ascorbic acid has been used as stabilizing agent/capping agent. Herein, a simple two steps wet-chemical method has been used for the synthesis of the nanocomposite A(NC). This synthesized nanocomposite has been characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). A comparative electrochemical study has been done using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques for supercapacitor performance. This study has been performed with a three-electrode system using 1 M Na₂SO₄ as a supporting electrolyte. Herein, a glassy carbon electrode (GCE) as a working electrode, Ag/AgCl as a reference electrode and Pt electrode as a counter electrode have been used in the electrochemical analysis. The CV curves have been recorded at different scan rates of 5 mV/s, 10 mV/s, 15 mV/s, 20 mV/s, 40 mV/s, 80 mV/s, and 100 mV/s respectively. The value of specific capacitance has been calculated 2.1472 F/g at 5 mV/s and energy density at 0.1074 Wh/kg using the CV curves. Whereas, specific capacitance and energy density have been determined 0.6833 F/g and 0.0342 Wh/kg respectively using the GCD method. Also, the photocatalytic degradation behavior of the synthesized nanocomposite A(NC) has been investigated against methylene blue (MB) dye. Herein, 89.88% MB dye has been degraded with synthesized nanocomposite A(NC) within 360 min in the presence of sunlight.     

Air plasma spray processing and electrochemical characterization of Cu-SDC coatings for use in solid oxide fuel cell anodes

Air plasma spraying has been used to produce porous composite anodes based on Ce_0.8Sm_0.2O_1.9 (SDC) and Cu for use in solid oxide fuel cells (SOFCs). Preliminarily, a range of plasma conditions has been examined for the production of composite coatings from pre-mixed SDC and CuO powders. Plasma gas compositions were varied to obtain a range of plasma temperatures. After reduction in H₂, coatings were characterized for composition and microstructure using EDX and SEM. As a result of these tests, symmetrical sintered electrolyte-supported anode-anode cells were fabricated by air plasma spraying of the anodes, followed by in situ reduction of the CuO to Cu. Full cells deposited on SS430 porous substrates were then produced in one integrated process. Fine CuO and SDC powders have been used to produce homogeneously mixed anode coatings with higher surface area microstructures, resulting in area-specific polarization resistances of 4.8 Ω cm² in impedance tests in hydrogen at 712 °C.     

Hybrid lead-acid battery with reticulated vitreous carbon as a carrier- and current-collector of negative plate

Bare reticulated vitreous carbon (RVC) plated electrochemically with thin layer of lead was investigated as a negative plate carrier- and current-collector material for lead-acid batteries. Hybrid flooded single cell lead-acid batteries containing one negative plate based on a new type (RVC or Pb/RVC) of carrier/current-collector and two positive plates based on Pb-Ca grid collectors were assembled and subjected to charge/discharge tests (at 20-h and 1-h discharge rates) and Peukert's dependences determination. The promising results show that application of RVC as carrier- and current-collector in negative plate will significantly increase the specific capacity of lead-acid battery.     

Fabrication of single-walled carbon nanotube/tin nanoparticle composites by electrochemical reduction combined with vacuum filtration and hybrid co-filtration for high-performance lithium battery electrodes

Hybrids consisting of single-walled carbon nanotubes (SWNTs) and tin nanoparticles are prepared on substrates as anode materials for lithium-ion batteries via two different techniques: (i) hybrid co-filtration by simultaneous vacuum filtration of SWNT/tin nanoparticle hybrid solutions and (ii) a combined technique comprised of vacuum filtration and electrochemical reduction. The resulting hybrid composites are of uniform thickness and consist of a homogeneous dispersion of tin nanoparticles in a SWNT network. In the hybrid films, the tin nanoparticles and SWNTs are in close contact with each other and the substrate. The hybrid films exhibit extended cycle life (capacity retention of 80% at 50th cycle), high power characteristics up to 1.75 mA cm⁻², high electrode density up to 5 mg cm⁻², and enhanced reversible capacities (535 mAh g⁻¹ for composite electrode at 50th cycle) because the aggregation of tin nanoparticles is prevented.