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Na-ion batteries are emerging as convenient energy-storage devices for large-scale applications. Enhanced energy density and cycling stability are key in the optimization of functional cathode materials such as P2-type layered transition metal oxides. High operating voltage can be achieved by enabling anionic reactions, but irreversibility of O2-/O2n-/O2 evolution still limits this chance, leading to extra capacity at first cycle that is not fully recovered. Here, we dissect this intriguing oxygen redox activity in Mn-deficient NaxNi0.25Mn0.68O2 from first-principles, by analyzing the formation of oxygen vacancies and dioxygen complexes at different stages of sodiation. We identify low-energy intermediates that release molecular O2 at high voltage, and we show how to improve the overall cathode stability by partial substitution of Ni with Fe. These new atomistic insights on O2 formation mechanism set solid scientific foundations for inhibition and control of this process toward the rational design of new anionic redox-active cathode materials.

The electrochemical storage sub-program is a part of a larger program, The Electrical System Research, aimed at developing technical and technological innovation of general interest for the Italian electricity sector. The sub-program is finalized to find new electrochemical energy storage technologies suitable for stationary applications. It intends to study innovative active material with the aim of reducing the preparation costs. To increase the energy density of lithium-ion battery, a combined approach is proposed, which synergistically exploits the properties of salts based on orthoborate anions and ionic liquids. Advanced computational modeling will enable rapid prototyping and screening of materials. At the same time, the replacing of the intercalation materials with materials capable of reacting with lithium by alloying or conversion processes will allow to increase the energy density of the devices. In order to improve the thermal stability and wettability of the separators the use of polymeric non-woven fabrics will be investigated. To foster the development of sodium ion battery study and development of cathode and anode materials that have a high specific capacity, good cyclic stability and high energy density will be carried out. As regards the electrolyte for sodium ion batteries, electrolyte systems based on organic and/or aqueous solvents will be designed. Innovative lithium metal batteries will be also investigated: the key to solving the problem of dendrite formation is reputed be the protection of the lithium anode. The basic idea is to develop a coating material or a gelled polymer electrolyte that can protect the surface of the lithium metal and make the deposition of lithium ions uniform, avoiding their preferential growth in some places. This would allow the development of technologies based on Li-metal/X electrochemical pairs in which X could be represented by S or O2.

In this work, by using an indirect method based on the correspondence between the amount of oxygen in the atmosphere and the quantity of fossil fuel in the Earth, the resources of fossil fuels were evaluated to be about 1.9 × 1016 ton. Unluckily, only a small part of these fuels is easily accessible. Nevertheless, their quantity is so high that it is reasonable to assume that fossil fuels will continue to dominate the global energy scene for several years. The extensive use of fossil fuels alters the ratio between oxygen and carbon dioxide in the atmosphere. The effects of this change are however so slow that they become important only on the geological time scale.

In this work we propose the use of a hydro-dispersible polymer such as the poly vinyl acetate as a binder for the production of electrodes for lithium-ion batteries. To increase the film forming properties of the polymer the poly vinyl was added with triacetin that acts as a plasticizer. The electrochemical stability of the polymer was tested by a polarizing electrode, formed by mixing the polymer with carbon. Subsequently, an electrode tape was prepared by using LiNi 0.5 Mn 1.5 O 4 as the active material and characterized by SEM, EDS and TGA. Lithium metal cells were assembled and tested to evaluate specific capacity, power and energy density at various discharge rates. The cycle life of the cell was evaluated by galvanostatic charge/discharge cycles. The tests showed that the electrodes prepared with PVA plasticized with triacetin have very good electrochemical performance in terms of capacity retention as a function of the discharge rate and the cycle number. Our work demonstrates that the use of triacetin to plasticize the PVA allows to increase the electrochemical stability of the electrode likely due to an improvement of the slurry filmability. The proposed method could represent a promising technology for the production of long-term performance lithium batteries.

Silicon (Si) nanowires (NWs) grown on stainless-steel substrates by Cu-catalysed Chemical Vapour Deposition (CVD) have been prepared to be used as anodes in lithium-ion batteries. The use of NWs can overcome the problems related to the Si volume changes occurring during lithium alloying by reducing stress relaxation and preventing material fragmentation. Moreover, since the SiNWs are grown directly on the substrate, which also acts as a current collector, an excellent electrical contact is generated between the two materials without the necessity to use additional binders or conducting additives. The electrochemical performance of the SiNWs was tested in cells using lithium metal as the anode. A large irreversible capacity was observed during the first cycle and, to a lesser extent, during the second cycle. All the subsequent cycles showed good reversibility even if the coulombic efficiency did not exceed 95%, suggesting the formation of an unstable SEI film and a continuous decomposition of the electrolyte on the silicon surface. The absence of a stable SEI film was assumed responsible for a linear capacity fade observed upon cycling. On the other hand, the electrochemical characterization performed at different values of the charging current showed that SiNWs possess an exceptionally high rate capability.

In this paper we want to show some of the most recent results obtained in our laboratory concerning the fabrication of lithium sulfur batteries. For their construction we used two different binders and two carbons with different surface areas, deposited directly on the separator. Sulfur was introduced mixed with the electrolyte in the form of polysulfide. The particular cell configuration has allowed to obtain stable specific capacities after numerous charge and discharge cycles of more than 800 and 1200mAh/g and low cell resistances.

This manuscript contains a survey of composite anodes for sodium ion batteries based on hard carbon obtained from different wood precursors. The hard carbon was activated with various metal hydroxide (MeOH with Me = Na, K, Rb, Cs). A commercially available carbon was also tested to compare the performance of the hard carbon so prepared. Electrochemical tests have shown that anodes prepared with different hard carbons have different specific capacities. The different capacity was related both to the type of wood used as the precursor and to the metal hydroxide used as the activation agent. The cycling tests indicated that KOH activated hard carbons show the best performance in terms of specific capacity and rate capability. The effect of the cation size on the carbon activation process can be explained considering that the alkali metal acts through a mechanism combined which on the one hand determines an increase in the porosity of the carbon and on the other one, an increase in the inter-atomic distance of the carbon structure.

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA&middot, h&middot, g&minus, 1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75O was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA&middot, 1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75O was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell&rsquo, s power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA&middot, 1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

This is the peer reviewed version of the following article: 1,3-Dioxolane: A Strategy to Improve Electrode Interfaces in Lithium Ion and Lithium-Sulfur Batteries, Andrea La Monaca, Francesca De Giorgio, Francesca Soavi, Gabriele Tarquini, Mariasole Di Carli, Pier Paolo Prosini, Catia Arbizzani, ChemElectroChem 2018, 5, 1272–1278, which has been published in final form at https://doi.org/10.1002/celc.201701348. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

In this paper a method for the synthesis of nano-sized microcrystalline LiFePO4, which is particularly suitable for the production of high energy density electrodes, was developed. The method is characterized by the fact that it provides for the solid state reaction of anhydrous FePO4 with lithium acetate. The method is easy to implement and, above all, does not involve the need to operate in a controlled environment, since the material may be synthesized directly in air by mixing anhydrous FePO4 with lithium acetate. This latter is simultaneously used as a reducing and lithiating agent. Anhydrous FePO4 is prepared by dehydrating iron phosphate hydrate, which is in turn prepared by means of the spontaneous precipitation thereof from a solution of FeSO4 and NaH2PO4, using H2O2 as the oxidizing agent. The FePO4 used as the precursor is characterized by thermogravimetry and its morphology is investigated by SEM microscopy. The structure of LiFePO4 is characterized by X-Ray diffraction and its morphology investigated by SEM microscopy. Finally, the LiFePO4 is used to fabricate composite electrodes that are electrochemical tested in lithium cells. © 2015 Elsevier B.V. All rights reserved.

The current state-of-the-art quantum mechanics methodologies were applied to derive information on the bulk and surface properties of the P2-type layered oxide Na0.85Li0.17Ni0.21Mn0.64O2 (NLNMO), a cathode material. The special quasi-random structure (SQS) approach was employed to identify the arrangement of Li, Ni, and Mn ions in a supercell containing 115 atoms. Both the cell parameters and atomic positions were determined from DFT-PBE+U calculations to highlight specific distortions induced by the dopants (Ni and Li). The analysis of atomic partial charges and atomic magnetic moments revealed that Li has a purely structural role, while Ni and Mn actively participate in both redox processes and electronic conduction. Using a new surface slab model, the interaction between the layered Na0.85Li0.17Ni0.21Mn0.64O2 (001) surface and the Na ions was examined to identify the most favorable adsorption sites and the possible paths for the migration of the Na ions on the electrode surface.

Recently, rechargeable Li S batteries, a next-generation energy storage system, are deeply studied due to their theoretical specific energy density. However, to produce batteries comparable to those already available on the market some drawbacks must be overcome, including essentially self-discharge, high internal resistance and rapid capacity fading upon cycling. In this work the use of polysulfide solutions either as additives or as active material in Li S batteries is proposed. The addition of polysulfides to the electrolytic solution improves the cell performances in terms of specific capacity and coulombic efficiency, passing from a capacity of about 150 mAh/g with a coulombic efficiency of about 0.85 to a capacity of 600 mAh/g with a coulombic efficiency of about 0.99 after 10 cycles. In batteries where polysulfide solutions are used as cathodic material, the obtained performances are even higher, reaching specific capacities of 420–450 mAh/g after about 70 cycles. Moreover, the cells tested with carbon paper as electrode support shows a greater reversibility, with a coulombic efficiency very close to 1. Finally, reducing the potential window from 3 to 1.5 V to 2.8–1.7 V, the cells show high stability and efficiency, reaching specific capacity values of about 600 mAh/g after 200 cycles.

Nanofibers produced by electrospinning show an interlaced and highly porous structure with a large surface-to-volume ratio. Such property makes the nanofibers useful in several applications such as healthcare, biotechnology, environmental engineering, defense & security, and energy storage. In this study polycaprolactone nanofibers have been tested as a mock-up separator in a lithium metal battery to evaluate the ion transport properties of ultrafine electrospun materials and assess the potential of this fabrication technology for lithium batteries. The membranes were soaked with an electrolyte solution and characterized by electrochemical impedance spectroscopy, finding that the porous structure of the polycaprolactone nanofiber membrane favors a complete and rapid uptake of the electrolyte. Furthermore, the large surface area of the nanofibrous network enhances ion conductivity, improving the power response of the polymer battery as compared with other polymer batteries. The electrochemical performance of a full battery was obtained on a prototype battery assembled by sandwiching the electrolyte-soaked nanofibrous membrane between a lithium anode and a LiFePO4 based cathode. The results showed that the battery can be discharged at high power with a good capacity retention. Despite intrinsic limitation of the polycaprolactone per se, the good performance of these membranes as separator certainly indicates that electrospinning is a relevant candidate method to develop and produce separators for high power batteries.

The very high theoretical capacity of the silicon (4200mAh/g more than 10 times larger than graphite), environmental-friendly, abundant and low-cost, makes it a potential candidate to replace graphite in high energy density Li-ion batteries. As a drawback, silicon suffers from huge volume changes (300%) on alloying and dealloying with Li, leading a structural deformation that induces disruption. The use of nanostructured silicon materials has been shown to be an effective way to avoid this mechanical degradation of the active material. In this paper the synthesis of silicon nanowires, grown on a highly porous 3D-like carbon paper substrate by CVD using Cu as the catalyst, is presented. The use of carbon paper allows to achieve remarkable loadings of active material (2-5 mg/cm2) and, consequently, high capacity densities. The silicon electrode was investigated both morphologically and electrochemically. To improve the electrochemical performance various strategies have been carried out. It was observed that a very slow first cycle (C/40), which helps the formation of a stable solid electrolyte interphase on the silicon surface, improves the performance of the cells; nevertheless, their cycle life has been found not fully satisfactory. Morphological analysis of the Si-NWs electrodes before and after cycling showed the presence of a dense silicon layer below the nanowires which could reduce the electrical contact between the active material and the substrate.

This paper describes the preparation and electrochemical characterization of Li-ion batteries prepared with electrodes containing non-fluorinated water dispersible polymers as electrode binders. Two commercial adhesives based on polyvinyl acetate and polystyrene acrylate, were used as the positive and negative electrode binders, respectively. The main advantages to using these polymers are related to their low cost, large diffusion, and negligible toxicity. Furthermore, since the polymers are water dispersible their use allows replacing the organic solvent, employed to dissolve the fluorinated polymer normally used as the binder in lithium battery technology, with water. In such a way it is possible to decrease the hazardousness of the preparation process as well as the production costs of both the electrodes. In the paper the preparation, characterization and the electrochemical performance of the Li-ion batteries obtained by coupling the two electrodes are described. © 2015 Elsevier Ltd. All rights reserved.

This paper describes the preparation and characterization of a high voltage composite cathode for lithium ion-batteries based on LiNi0.5Mn1.5O4 as the active material and poly vinyl acetate (PVAc) as the binder. To assess the effect of the PVAc binder on the electrode properties, the PVAc-based electrode is compared with a traditional one prepared by using Teflon as the binder. The electrode morphologies are investigated by scanning electron microscopy and the thermal behavior of the PVAc-based electrode evaluated by thermo gravimetry and differential thermal analysis. The distribution of oxygen, manganese, and nickel on the electrode is investigated by X-ray electron diffraction spectroscopy. The electrodes are used as cathodes to prepare lithium metal cells and their electrochemical properties are investigated through galvanostatic charge/discharge cycles conducted at various discharge currents. © 2015 Elsevier B.V. All rights reserved.

During the last years, with the development of the battery technology, besides Li-ion batteries, Na-ion batteries have been extensively studied as well. However, some disadvantages and issues, such as the impossibility to use the graphite as anode material, are still to be overcome. At the same time, environmental problems push researchers to develop practical and convenient ways to perform useful materials recycling. In this context, the present work evaluates an innovative high pressure water jet recycling process of tires to produce a carbon material to be used as anode in alkali ion (Li, Na) batteries. Prior to be used, the carbon was washed with a solution of sulfuric acid and then pyrolysed. This obtained material was characterized by using SEM and EDX analysis, while a preliminary electrochemical characterization has been performed by charge/discharge cycles in galvanostatic mode at C/10 rate. A comparison between Li and Na intercalation has been carried out. For Li-ion batteries capacities of about 290 mAh g−1 have been obtained, while for Na-ion batteries a capacity of 140 mAh g−1 has been achieved.

In order to implement a Li/S semiflow battery, a mixture of lithium polysulfide (Li2S8) dissolved in dioxolane/dimethoxyethane was studied as a catholyte in Li/carbon battery cells. The Li2S8 polysulfide was prepared by stirring Li2S and elemental sulfur in a 1:1 mixture of dioxolane/dimethoxyethane heated at 80 °C. The mixture of polysulfides was tested in a lithium metal cell. The working electrode was a mixture of Ketjenblack carbon (used as conductive filler) and PTFE. It was found the Li2S8 polysulfide immediately converts into Li2S4 and sulfur when added to the electrolyte solution. The electrochemical tests showed that the cell retains excellent Coulombic efficiency and good cycling stability. The potential window used during the electrochemical tests plays an important role on the cell performance in terms of stability and capacity. An improvement of more than 500 mAh g−1 in the specific capacity retention was observed when the potential window was reduced from 3.0–1.5 V to 2.8–1.7 V. Post mortem SEM and EDS analyses confirmed that not only the surface but the whole of the working electrode participates to the electrochemical reaction. © 2018 Elsevier B.V.

Magnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350 o C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. Composite formation with Zr based laves phase alloys, especially ZrCr2 family, is an effective method to improve the hydriding properties of MgH2. This work presents the synthesis, structural, morphological, and hydrogenation properties of Mg-x wt% ZrCrMn composites. Both phases i.e. Mg & ZrCrMn remain their presence after milling and several hydriding cycles as well. SEM results suggest the homogeneous distribution of alloy particles on Mg matrix. Pressure composition temperature (PCT) analysis shows a reduction in desorption temperature down to 250 o C for these composites. TG experiments suggest a total hydrogen capacity of 5.9% and 4.35% for x =25, 50 in Mg-x wt% ZrCrMn composites respectively. The enthalpy of hydride formation is also calculated using Van't Hoff plots, which is found similar to the parent material i.e. MgH2. A remarkable enhancement in the kinetics of hydrogen absorption / desorption is reported here by forming these composites. Copyright © 2014 VBRI press.

Three materials based on sodium iron phosphate with a Maricite structure were synthesized by hydrothermal method and solid-state synthesis. The materials have been characterized by X-ray diffraction, thermal analysis, and surface analysis. The materials were used for the fabrication of electrodes and their electrochemical performance were evaluated in lithium batteries. The material with the highest reversible capacity was then characterized in sodium batteries. Both the capacity exhibited at low discharge rate as well as the capacity as a function of the discharge rate and cycle number were evaluated. The obtained values were used for the determination of the specific energy as a function of the specific discharge power. At the lower discharge rate (C/20), the material was able to deliver 52.0 mAh g- 1 with an average charge voltage of 2.5 V corresponding to a specific energy of 130 Wh kg- 1. The specific capacity recorded at the lowest discharge rate gradually increased with the number of cycles and reached a value of 63 mAh g- 1 at the 150th cycle. © 2014 Elsevier B.V.

In this paper the preparation of silicon nanowires and their electrochemical characterization as an anode in lithium batteries is reported. The nanowires were synthesized by CVD and characterized by XRD, SEM and EDS. The nanostructured materials were used as electrodes in lithium cells and their electrochemical properties were investigated by galvanostatic charge-discharge cycles at various discharge rates. To evaluate the dependence of the specific capacity and charge coefficient on the end charge potential this parameter was varied during the experimentation. The evolution of the charge transfer resistance, specific capacity, and charge coefficient as a function of the number of the cycles was also investigated. © 2014 Elsevier B.V. All rights reserved.

We have optmized the electrode blend composition and tape preparation for Li-S batteries. Ethylene vinyl acetate (EVA), an hydro dispersible polymer was employed as a binder. This allows an aqueous preparation route for the composite cathode, promoting a more eco-friendly and economical productive process. Various conductive substrates have been compared: the EVA based blend have been deposited on aluminium, carbon paper and carbon cloth sheets. The electrode morphology of the electrode was evaluated by scanning electron microscopy (SEM) and thermal stabilitiy was tested by TGA. Electrochemical testing was performed in coin cells by using lithium metal as the counter and the reference electrodes. Among the others, the electrodes realized by using ketjen black carbon and EVA showed higher specific capacity and Coulombic efficiency, of 900 mAhg-1 after 50 cycles and 99 %, respectively. This study showed that EVA represents a promising binder for the development of high capacity Li-S batteries.

In this paper the preparation, the morphology, the structure and the electrochemical performance of carbon coated TiO2 produced by using Tyzorﾮ-LA as a precursor have been studied by using SEM, XRD and electrochemical methods. The electrochemical methods included low rate cycling, cycling at C-rate and cycling at different rates. At the same time the physical and electrochemical properties of LiFePO4 were investigated by using the same methods. Lithium-ion batteries were prepared by sandwiching a glass fiber between a TiO2 electrode used as the anode and a LiFePO 4 electrode used as the cathode and tested to evaluate cell performance. ﾩ 2013 Elsevier B.V. All rights reserved.

To evaluate the possibility of using nanosized TiO 2 to replace the carbonaceous materials usually employed as the negative electrode of lithium-ion batteries, we studied and compared the electrochemical performance of TiO 2 nanotubes with a commercial material (P25 Degussa). TiO 2 nanotubes were prepared by electrochemical anodization of titanium sheets. The nanotubes were characterized by using SEM and XRD. Composite electrode tapes were made by roll milling the TiO 2 nanotubes and the TiO 2 P25 Degussa with carbon and Teflon. The electrodes were electrochemical characterized in lithium cell by charge/discharge cycles. The electrochemical tests comprised low rate cycling, cycling at C/rate and cycling at different rates.

In this paper the morphological, structural and electrochemical properties of crystalline lithium iron phosphate (LiFePO4) obtained from ferrous ammonium phosphate (FAP) have been studied. The FAP was obtained following four different processes, namely: (1) homogeneous phase precipitation, (2) heterogeneous phase precipitation from stoichiometric sodium phosphate, (3) heterogeneous phase precipitation from stoichiometric ammonium phosphate, and (4) heterogeneous phase precipitation from over stoichiometric ammonium phosphate. Lithium iron phosphate was prepared by solid state reaction of FAP with lithium hydroxide. In order to evaluate the effect of reaction time and synthesis temperature the LiFePO4 was prepared varying the heating temperatures (550, 600 and 700 C) and the reaction times (1 or 2 h). The morphology of the materials was evaluated by scanning electron microscopy while the chemical composition was determined by electron energy loss spectroscopy. X-ray diffraction was used to evaluate phase composition, crystal structure and crystallite size. The so obtained LiFePO4's were fully electrochemical characterized and a correlation was found between the crystal size and the electrochemical performance. © 2013 Elsevier Ltd. All rights reserved.

Ethylene vinyl acetate, a hydro dispersible polymer largely used in the plastic industry, was employed as a polymer binder for the fabrication of the positive electrode of lithium-ion batteries. LiNi0.5Mn1.5O4 was used as the active material. The electrode was prepared by painting a thin aluminum sheet with a suspension obtained by mixing the carbon, the active material, and the polymer in water. The electrode was first analyzed from a chemical-physical point of view. The electrode morphology was evaluated by scanning electron microscopy (SEM) and the surface chemistry mapped by energy dispersive X-ray spectroscopy (EDS). The thermal stability was tested by heating the electrode in air using a simultaneous TG-DTA. The anodic stability of the polymer was examined versus a lithium anode. Finally the electrode was used to prepare a two electrodes lithium cell and the cell was tested to evaluate the electrode capacity retention as a function of the applied current and cycle number. The electrochemical properties of the electrode have been found very promising for the realization of high energy, high power, long cycle life batteries being capable of cycling for hundreds of cycles with excellent performance and reduced loss of capacity. © 2016 Elsevier B.V.

With the purpose of increasing the net energy balance of Brassica carinata we hereby propose to recover, in addition to oil from seeds, furfural from straws. To evaluate the net energy yield of transformation, about 600 plants of B. carinata have been cultivated and 100 randomly selected plants analyzed. Seeds and straws were divided, weighed and used for oil and furfural extraction, respectively. The oil content ranged from 2.5 up to 40 g per plant with a mean value of 19.6 g. The quantity of extracted oil resulted strictly correlated to seed weight rather than to oil percentage in the seed. The straw weight ranged from 450 up to 625 g per plant with a mean value of 500.6 g. Furfural was produced with a yield of 6.4% from fresh weight straw. Oil and furfural productivity per hectare were calculated from the obtained mean values per plant. It was found that the energy content in the furfural is similar to that of oil. The furfural production increases the overall energy yield of conversion from 7.1% (calculated considering only the oil from the seeds) up to 13.8% (calculated considering the oil from the seeds plus the furfural from the straws). The steam needed for furfural production and purification can be obtained by burning about one half of the cellulose and lignin, obtained as byproduct after straw processing for furfural extraction. Furfural can be hydrogenated to produce tetrahydrofurfuryl alcohol a renewable bio-fuel of new generation with chemical–physical characteristics very similar to those of kerosene.

Magnesium hydride has a high theoretically storage capacity, which amounts to 7.6 wt%. It is therefore a promising candidate for hydrogen storage applications. However, its major drawback is its high desorption temperature of well over 300 °C, which is related to the high stability of the Mg–H bonds and expressed in the high enthalpy of hydride formation (77 kJ/mol). The preparation of Mg composites with other hydrogen storage compounds is an effective method to improve the hydrogen storage properties of Mg. Thus we prepared Mg-50 wt% ZrCrFe alloy composite by high energy ball milling under argon atmosphere. X-ray diffraction (XRD) studies on the composite before and after hydriding cycles suggest no intermetalic phase is formed between Mg and the elements of the alloy. The morphological studies carried on by Scanning Electron Microscope (SEM) technique suggest that the alloy particles are homogeneously distributed throughout the Mg surface. A particle reduction after hydrogenation is also visible. Hydriding/dehydriding properties of the composites are investigated by PCT measurements using a dynamic system. The maximum hydrogen capacity for this composite is found to be 4.5 wt%. The reaction kinetics have also been recorded in a temperature range from RT to 300 °C and the thermodynamic parameters calculated from Van’t Hoff plot. From the results it is found that the alloy reacts with hydrogen also when cooled to room temperature while at higher temperature it works as catalyst.

Chemical hydrides have already been pointed out as great potential hydrogen storage materials. In this paper, the hydrolysis of two solid hydrides, namely sodium borohydride (NaBH4) and lithium hydride (LiH) was studied to check their performance as hydrogen generators. The simplicity of the reactor design, the absence of high pressure or very high temperatures as well as the benignity of the spent fuel make this hydrogen storage approach conceptually feasible. Several devices have been developed and tested. The devices have been designed to generate hydrogen flows in the 0.5–1.0 L min−1 range. Batches up to 500 g of sodium borohydride powder were hydrolyzed with liquid water. 10.0 wt. % nickel acetate was used as catalyst. Hydrogen flows in the desired range have been continuously produced for several hours (up to 30 h). Due to the high reactivity lithium hydride was hydrolyzed without any catalyst. In this case batches of about 50 g have been hydrolyzed with steam for 4 h.

In this paper nickel acetate catalyzed sodium borohydride cartridges have been prepared and hydrolyzed with water for hydrogen production. Two technological solutions have been tested to increase the overall hydrogen yield, namely a porous water diffuser and a hydrophobic membrane. The first was used to improve water diffusion inside the hydride while the second to confine water inside the cartridge. The generated hydrogen flow showed a very reproducible behavior. Hydrogen promptly evolved just after water was pumped into the cartridge. After some initial peaks, a constant hydrogen flow has been recorded for the whole reaction time. The constant flow was related to the presence of the porous diffuser. The use of a hydrophobic membrane to confine the water inside the cartridge allowed to increase the overall hydrogen yield: about 6 water molecules per mol of hydride were required to complete the reaction. The reaction product was identified by XRD as Na2B2O4*8H2O. The cartridge hydrogen gravimetric content, based on water and sodium borohydride weight, was as high as 4.64%.

Steam hydrolysis of lithium hydride was studied at various temperatures (20°C–80°C). To monitor the reaction rate, hydrogen flow was recorded as a function of time. Phase composition of the reaction products was analyzed by XRD spectroscopy. A variation in the reaction mechanism was found for temperatures lower than 70°C when lithium hydride was reduced to 10% of the initial amount. Using XRD analysis it was found that the main product obtained at temperatures ranging from 20°C to 70°C was LiOH.H2O. By increasing the temperature, the percentage of dehydrate slowly increases, and at 80°C the dehydrate represents the main product. A simple model for steam hydrolysis of lithium hydride is proposed taking into consideration the experimental results. The behavior of hydrogen flow was related to water vapor pressure and unreacted lithium hydride amount. The change in the reaction mechanism was related to a variation of water uptake (from the solid phase to the gas phase) to the lithium hydride surface.

A large excess of water and iodine is typically employed in the Bunsen reaction step of the sulfur–iodine thermochemical cycle in order to induce liquid–liquid phase separation of the two acid products. This paper presents an overview of some alternative routes for carrying out the Bunsen reaction. The use of a reaction solvent other than water is first discussed, and experimental results obtained with tributylphosphate are presented. Another approach is separation of the product acids by selective precipitation of insoluble salts, and the addition of lead sulfate as the precipitating agent is discussed in detail. Finally, the electrochemical Bunsen reaction route is investigated. All of these methods have the potential to reduce the iodine and/or water requirement of the sulfur–iodine cycle.

The hydrolysis of sodium-borohydride (SBH) to produce hydrogen has been studied at various temperatures using salts of nickel (II) or iron (III) as catalyst. Excess of water has been added to a mixture of solid SBH and catalyst to start hydrolysis reaction and the evolved hydrogen measured as a function of time. After a sudden peak a constant hydrogen flow was observed when Ni is used as catalyst. The activation energy has been evaluated from the dependence of the reaction time and of the hydrogen flow on the inverse of temperature. If Ni is substituted by a Fe based catalyst, after the initial increase, a different shape is observed in the hydrogen flow: it reaches a maximum and then monotonously decrease to zero. The different shape has been related to the different activity of the catalyst. The reaction activation energy was evaluated to be 73 KJ/mol.

A thermochemical water-splitting cycle representing a modification of the classical sulphur–iodine cycle is proposed. To decrease the energetic demand, increasing the cycle energy efficiency, the distillation of the iodine phase was replaced with the evaporation of the excess of water and iodine. This was obtained by neutralizing the hydrogen iodide in the iodine phase with nickel oxide. In such a way water and iodine can be simply recovered by evaporation leaving nickel iodide as solid phase. The nickel iodide is decomposed to obtain nickel metal and hydrogen is produced by reaction of the metal with sulphuric acid. The nickel sulphate, obtained after hydrogen production, is decomposed to generate sulphur dioxide (used as the reagent in the Bunsen reaction) and nickel oxide (that is recycled). To validate the cycle effectiveness the proposed reactions have been carried out. Crystalline solid materials have been identified by XRD diffraction. Powders morphology was studied by scanning electron microscopy and energy dispersive X-ray. Thermodynamics studies were carried out by thermogravimetric and differential thermal analysis. Finally an energy balance to evaluate the theoretical energy efficiency was computed.

A system for a controlled production of hydrogen from solid NaBH 4 has been designed and built. Cartridges of catalysed or non-catalysed NaBH 4 in powder form are fed by water or catalyst solution into a reactor; the reaction is started and tuned by controlling the input water (or water/catalyst solution) flow. We designed, built and tested different reactor layouts and geometries. Tests have been carried out in order to monitor operative parameters (i.e., water flow, reactor temperature) and to evaluate their influence on hydrolysis performance. The facility allows hydrogen flow in the 5–30 L/h range for several hours. The paper reports on the experimental runs and on the main achieved goals.

Fitting of the voltage vs. insertion curves of the LiFePO4 electrode was based on theoretical expressions describing the Li+ diffusive process in a solid medium. The noninteracting gas model for the chemical potential of ions distributed in a solid matrix was taken into account, and the diffusion coefficient and the energy activation for the diffusion process were accordingly calculated. The polarization curves at various discharge stages were theoretically obtained, and a good agreement was found with the experimental data at all discharge rates. A mathematical relation describing the trend of the diffusion resistance vs. insertion degree was also developed.