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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.

In this paper, the methods used to enhance the conductivity of LiBH4, a potential electrolyte for the construction of solid-state batteries, are summarized. Since this electrolyte becomes conductive at temperatures above 380 K due to a phase change, numerous studies have been conducted to lower the temperature at which the hydride becomes conductive. An increase in conductivity at lower temperatures has generally been obtained by adding a second component that can increase the mobility of the lithium ion. In some cases, conductivities at room temperature, such as those exhibited by the liquid electrolytes used in current lithium-ion batteries, have been achieved. With these modified electrolytes, both lithium metal and lithium-ion cells have also been constructed, the performances of which are reported in the paper. In some cases, cells characterized by a high capacity and rate capability have been developed. Although it is still necessary to confirm the stability of the devices, especially in terms of cyclability, LiBH4-based doped electrolytes could be employed to produce solid-state lithium or lithium-ion batteries susceptible to industrial development.

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.

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.

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.

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.

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.

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.

A modification of the conventional Sulfur–Iodine (S–I) thermochemical water-splitting cycle (TWSC) by means of double exchange reactions (metathesis) is presented. In conventional S–I TWSC an excess of water and iodine has to be used for phase separation and a large amount of heat is requested for water and iodine evaporation. To reduce the amount of these chemicals we propose the formation of solid phases obtained by using lead as the precipitating agent. The obtained solid can be easily separated from the liquid by filtration avoiding evaporation processes. The formation of anhydrous gases allows to minimize corrosion problems and to reduce heat demand during hydrogen iodide decomposition.

A device has been designed to generate hydrogen for a fuel cell powered cellular phone. The device is based on the chemical reaction between NaBH 4 and hydrochloric/water solution to satisfy the hydrogen request at room temperature and pressure. The operation mechanism and controlling method is based on the Kipp's gas generating apparatus. A prototype has been built and tested to evaluate the optimum salt/acid and acid/solution ratios and check the hydrogen mass flow rates upon operation and the pressure variation in stand-by condition. The system works delivering hydrogen flows ranging between 0 and 10 ml min −1 . In a typical test the hydrogen flow was set to 5 ml min −1 to match a 1 W power fuel cell. The working pressure was slightly higher than the atmospheric one. The hydrogen capacity was as high as 2.5% (w/w). By converting this amount of hydrogen in electricity by a fuel cell working at 0.8 V it is possible to achieve a system energy density of about 720 Wh kg −1 , four times larger than commercial high energy density lithium-ion batteries.

The cycle behaviour and rate performance of solid-state Li/LiFePO 4 polymer electrolyte batteries incorporating the N -methyl- N -propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 13 TFSI) room temperature ionic liquid (IL) into the P(EO) 20 LiTFSI electrolyte and the cathode have been investigated at 40 °C. The ionic conductivity of the P(EO) 20 LiTFSI + PYR 13 TFSI polymer electrolyte was about 6 × 10 −4 S cm −1 at 40 °C for a PYR 13 + /Li + mole ratio of 1.73. Li/LiFePO 4 batteries retained about 86% of their initial discharge capacity (127 mAh g −1 ) after 240 continuous cycles and showed excellent reversible cyclability with a capacity fade lower than 0.06% per cycle over about 500 cycles at various current densities. In addition, the Li/LiFePO 4 batteries exhibited some discharge capability at high currents up to 1.52 mA cm −2 (2 C) at 40 °C which is very significant for a lithium metal-polymer electrolyte (solvent-free) battery systems. The addition of the IL to lithium metal-polymer electrolyte batteries has resulted in a very promising improvement in performance at moderate temperatures.

The thermal decomposition of borane–ammonia complex as well as of milled and doped samples was studied by volumetric titrations. The samples were heated at fixed temperature and the volume of the evolved gas recorded as a function of time. Milled and doped samples were prepared by mechanical and mechanochemical reactions, respectively. Samples containing 1 and 2 mol% hydrogen hexachloroplatinate hydrate were prepared. The materials were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Mechanical alloying was effective to modify the crystallinity of the complex and to change the material morphology enhancing the amount of gas evolved. Both the milled and the doped samples showed an increase of the pre-exponential factor in the Arrhenius equation. The activation energy decreased for the doped sample, and it increased for the milled sample. As a result it was found that the decomposition of 1 mol% doped sample could be provided by waste heat coming from polymer electrolyte membrane fuel cell.

The thermal behaviour of commercial Carbolex single-walled carbon nanotubes (SWCNTs) both as-received and after purification by a novel method has been studied by thermogravimetric/derivative thermogravimetric/difference thermal analysis (TG/DTG/DTA). Purification from metal catalysts (Ni and Y) has been successfully obtained using 0.1 M I 2 in iso-propanol instead of the usual concentrated HNO 3 . The final residues of thermal analysis have been characterised by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The gathered results showed that the as-received SWCNTs burns out in a one-step between 573 and 923 K, whereas the SWCNTs treated with HNO 3 become highly hygroscopic. The I 2 -iso-propanol-treated SWCNTs showed three overlapped exothermic peaks between 500 and 973 K in the DTA curve, which allowed separating amorphous carbon from SWCNTs by air-thermal treatment at 573 K. The graphite-like compounds, which are present in both untreated and treated SWCNTs, does not burn up to 1173 K.

0.4 Ah lithium-ion battery prototypes, developed within a national project devoted to development of power sources for consumer applications, have been fabricated and tested. A novel, intrinsically porous, PVdF–HFP/MgO composite separator, capable to be hot-laminated onto PVDF–HFP-based electrodes without losing its ability to retain liquid electrolyte, was developed. The devices were assembled by direct lamination of the components, namely graphite anode tapes, PVDF–HFP/MgO separators and LiMn2O4 cathode films. The prototypes, formed by a stack of 12 single cells connected in parallel, need no external pressure to maintain contact between the layers. The battery performance was evaluated in terms of capacity, cycle life, energy and power density at different rates. The capability of prototypes to uptake liquid electrolyte was also investigated. The results have indicated the feasibility to scale-up lithium-ion cells to manufacture 0.4 Ah class battery prototypes showing good cycling performance.

LiFePO 4 /C composites were prepared by using organo-phosphonates as a single source of iron, phosphorus and carbon. Fe[RPO 3 ].H 2 O (R = methyl or phenyl group) was heated in the presence of Li 2 CO 3 at high temperature and under nitrogen flux. Elemental carbon is formed on the surface of LiFePO 4 particles leaving a carbon coated material. The materials were characterized by elemental analysis, TG/DTA, XRPD and SEM. Coulometric titration showed that some impurities are present in the final products. The material prepared starting from the iron(II) phenyl phosphonate showed higher discharge capacity, specific energy, and specific power. The specific energy evaluated at C/10 rate was about 520 Wh kg -1 . The specific power calculated at 3C rate was in excess at 1400 W kg -1 while the specific energy was about 63% of the energy delivered at C/10. No capacity fading was observed upon cycling. The performance of LiFePO 4 prepared from the iron(II) methyl phosphonate was found to be slightly lower, probably due to the lower carbon content.

Undoped lithium iron phosphate (LiFePO 4 ) was prepared and characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The material has a single crystal globular structure with grain-sizes ca. 100–150 nm. It was used to prepare composite electrodes containing different amounts of carbon (10, 15 and 20 wt.%, respectively) used as cathodes in non-aqueous lithium cells. By increasing the carbon content, an increase in the overall electrochemical performance was observed. Impedance spectroscopy was used to investigate the ohmic and kinetic contributions to the cell overvoltage. It was found that increasing the carbon content leads to a reduction of the cell impedance as a consequence of the reduction of the charge transfer resistance. The poor performance exhibited at very high discharge rates is a direct consequence of the high value of the charge transfer resistance. A further decrease of the charge transfer resistance in high carbon content cathodes (20 wt.% carbon) was obtained by improving the powder mixing procedure. The cell performance of well mixed, high carbon content electrodes was better than our previously obtained results in terms of higher capacity retention both for different discharge rates and repeated cycling. For currents larger than a 3 C rate, a severe capacity fade affected the electrodes. It was concluded that the electronic contact at the LiFePO 4 /carbon interface plays a decisive role in material utilization at different discharge rates which affects the capacity fade upon cycling.

Amorphous iron(III) phosphate has been synthesised by homogeneous precipitation from equimolecular Fe(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O and NH 4 H 2 PO 4 aqueous, water–ethanol and water– iso -propanol solutions at pH=2.0 and ambient temperature using hydrogen peroxide as precipitating agent. The precipitates have been characterised by TG/DTG/DTA techniques, chemical analysis, X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM). The presence of ethanol and iso -propanol in the precipitation medium suppressed the co-precipitation of ferric sulphate as it does in aqueous medium. Thermal treatment of the as-precipitates at 750 °C in air yields a crystalline quartz-like structured FePO 4 with markedly different morphological features.

Amorphous LiFePO4 was obtained by lithiation of FePO4 synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH4)2(SO4)2·6H2O and NH4H2PO4, using hydrogen peroxide as oxidizing agent. Nano-crystalline LiFePO4 was obtained by heating amorphous nano-sized LiFePO4 for different periods of time. The materials were characterized by TG, DTA, X-ray powder diffraction, scanning electron microscopy (SEM) and BET. All materials showed very good electrochemical performance in terms of energy and power density. Upon cycling, a capacity fading affected the materials, thus reducing the electrochemical performance. Nevertheless, the fading decreased upon cycling and after the 200th cycle the cell was able to cycle for more than 500 cycles without further fading.

Microstructural variations of amorphous FePO4 and LiFePO4 (the latter obtained by chemical lithiation of the former) as a result of the annealing temperature have been studied by Thermogravimetric Analysis (TGA)/Differential Thermal Analysis (DTA), chemical analysis, Brunauer–Emmet–Taylor (BET) and Scanning Electron Microscopy (SEM) techniques. Round-shaped amorphous FePO4 particles 40–80 nm in size are obtained after heating (at 400 °C) amorphous FePO4·2H2O in air (previously prepared by a precipitation route). On further heating at 650 °C, in air, crystalline trigonal FePO4 of crystallite size

Carbon nanotube films produced on a Si(1 0 0) substrate without any metal catalyst were used as electrodes in galvanic cells. The electrochemical mechanism of hydrogen evolution, storage and oxidation was studied using cyclic voltammetry and galvanostatic polarisation. Cyclic voltammetry showed that hydrogen is easily produced on the carbon nanotube surface, but a significant overvoltage was observed for hydrogen oxidation. The kinetics of hydrogen evolution influenced the quantity of hydrogen stored in the nanotube, which increased with increasing discharge currents.

Fe3(PO4)2·8H2O has been precipitated under supersaturation conditions from deaerated Fe(NH4)2(SO4)2·6H2O and K2HPO4 aqueous, ethanol–water and iso-propanol–water solutions at pH=6.5 and ambient temperature. The precipitates have been characterised by TG/DTG/DTA and DSC techniques, chemical analysis, BET, and X-ray powder diffraction. The presence of ethanol and iso-propanol in the spontaneous precipitation process of ferrous phosphate leads to highly crystalline powder. Thermal treatment at 500 °C yields a poorly crystalline dehydrated iron phosphate.

γ-LiAlO2, Al2O3 and MgO were used as fillers in a PVdF-HFP polymer matrix to form self-standing, intrinsically porous separators for lithium-ion batteries. These separators can be hot-laminated onto the electrodes without losing their ability to adsorb liquid electrolyte. The electrochemical stability of the separators was tested by constructing half-cells with the configuration: Li/fibre-glass/filler-based separator/electrode. MgO-based separators were found to work well with both positive and negative electrodes. An ionic conductivity of about 4×10−4 S cm−1 was calculated for the MgO-based separator containing 40% 1 M solution of LiPF6 in an EC/DMC 1:1 solvent. Self-standing, lithium-ion cells were constructed using the MgO-based separator and the resulting battery performance evaluated in terms of cyclability, power and energy density.

In this paper we report the electrochemical characterization of mixtures of ball-milled lithium nitride and iron metal. Several samples were prepared with different lithium nitride to iron molar ratios. X-ray diffraction (XRD) spectra showed the presence of iron metal in all the samples and β-lithium nitride in the samples with higher Li3N/Fe ratio. No evidence of other phases was detected. The milled powders were used to prepare composite cathodes for the electrochemical characterization. It was found that lithium can be extracted from the materials at a flat potential of 1.2 V vs. Li. The sample with Li3N/Fe molar ratio 8:1 showed the highest specific capacity (1125 mAh g−1) corresponding to the extraction of 1.8 Li equivalents per mole of lithium nitride. Only a fraction of the lithium extracted was re-inserted in the following discharge cycle. A drastic reduction of the capacity was observed for all the samples on further cycling. An enhancement of the cyclability was obtained by lowering the end-charge voltage that resulted in a reduction of the lithium extracted. The lithium extraction/insertion process was characterized by a large voltage difference indicating that the reaction is largely irreversible. Keywords: β-Lithium nitride, Mechanical alloying, Lithium battery, Anode material

The lithium insertion in the ordered olivine-type structure of LiFePO 4 was analyzed as an insertion process with a Frumkin-type sorption isotherm. A minimum in the chemical diffusion coefficient of lithium ( D Li ) was predicted by the model for strong attractive interactions between the intercalation species and the host matrix. The D Li in the material was measured as a function of the lithium content by using the galvanostatic intermittent titration technique (GITT). The diffusion coefficient was found 1.8×10 −14 and 2.2×10 −16 cm 2 s −1 for LiFePO 4 and FePO 4 , respectively, with a minimum in correspondence of the peak of the differential capacity. The D Li has also been measured by AC impedance method for various lithium contents. The calculated values are in very good agreement with the previous calculated ones.

Iron(III) phosphate has been precipitated under supersaturation conditions from equimolecular aqueous solutions of 0.025 M Fe(NO3)3·9H2O and K2HPO4, at pH=2.00 and at ambient temperature. The precipitate has been characterised by TG/DTG/DTA and DSC techniques, chemical analysis, IR-spectroscopy and X-ray powder diffraction. A yellowish-white amorphous solid of formula Fe2(HPO4)3·xH2O has been obtained. Alternatively, a pinkish-white amorphous precipitate of formula FePO4·2H2O is obtained under the same conditions from Fe(NH4)2(SO4)2·6H2O using hydrogen peroxide as the oxidising agent. Although the IR spectra and the thermal behaviour of both compounds are quite different, they crystallise as FePO4 when annealed at 650 °C in air.

Gel polymer electrolytes (GPEs) were prepared by dipping a polyethylene oxide (PEO)-based solid polymer electrolyte in lithium triflate/propylene carbonate (PC) liquid electrolyte solutions. The quantity of the liquid electrolyte gelled in the polymer was monitored as a function of dipping time in several liquid electrolytic solutions characterized by a different salt concentration. The GPE conductivity was measured as a function of the salt concentration and the liquid fraction content. The Li/GPE interface properties were evaluated by monitoring the charge transfer resistance at open circuit voltage and the lithium cycling efficiency under dynamic conditions. Chronopotentiometry measurements were used to study the variations of the lithium ion concentration in the electrolyte near the electrode surface. The transition time and the lithium diffusion coefficient were calculated as a function of the salt concentration of the liquid electrolyte used to swell the polymer electrolyte. The GPE electrochemical stability was measured by slow scan voltammetry sweep. Battery cells were assembled by sandwiching a GPE between a lithium disk and a gelled PEO-based composite cathode. The battery performance was evaluated at various discharge rates, while the rechargeability was tested under galvanostatic conditions at the C/10 rate.

Spinel Li 4 Ti 5 O 12 was prepared and tested as alternative anode for lithium-ion batteries. The electrochemical performance of the material was evaluated in liquid electrolyte at C/25 rate. The material delivered 150 mA h g −1 with a very satisfactory capacity retention. The electrochemical performance of commercial LiMn 2 O 4 was also tested. These materials were used to prepare polymer electrodes on aluminium foil substrate by using a screen-printing deposition technique. The transport properties of symmetrical polymer-electrode/polymer-electrolyte cells were evaluated by AC impedance. All-solid-state, plastic, lithium-ion batteries were fabricated with the cell configuration Li 4 Ti 5 O 12 /polymer electrolyte/LiMn 2 O 4 . The electrochemical performance of such a cell was evaluated at various temperatures.