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This work aimed to predict the crystal structure of a compound starting only from the knowledge of its chemical composition. The method was developed to select new materials in the field of lithium-ion batteries and tested on Li-Fe-O compounds. For each testing compound, the correspondence with respect to the training compounds was evaluated simply by calculating the Euclidean distance existing between the stoichiometric coefficients of the elements constituting the two compounds. At the compound under test was assigned the crystal structure of the training compound for which the distance value was minimum. The results showed that the model can predict the crystalline group of the test compound with an accuracy higher than 80% and a precision higher than 90%, for a cut-off distance higher than four. The method was then used to predict the crystalline group of manganese-based compounds (Li-Mn-O). The analysis conducted on twenty randomly selected compounds showed an accuracy of 70%. Out of ten valid predictions, nine were true positives, with a precision of 90%. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

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. more...

In this paper the synthesis and characterization of silicon nanowires to be used as the anode of a lithiumion battery cell are reported. The nanowires were synthesized by CVD and characterized by SEM. The nanostructured material was used as an electrode in a lithium cell and its electrochemical properties were investigated by galvanostatic charge/discharge cycles at C/10 rate as a function of the cycle number and at various rates as a function of the charge current. The electrode was then coupled with a LiFePO4 cathode to fabricate a lithium-ion battery cell and the cell performance evaluated by galvanostatic charge/discharge cycles. © 2015 AIP Publishing LLC. more...

This paper describes a method for the preparation of a composite anode for lithium ion-battery using a commercial non-fluorinated water-dispersible polymer (Pattex PL50) as a binder. The benefits offered by using this polymer are related to its low cost and negligible toxicity. Furthermore, since the polymer is water dispersible, its adoption allows to replace the organic solvents, traditionally used in lithium-ion battery technology, with water thus decreasing the hazardousness of the preparation process as well as the production costs of the electrodes. In this paper, the preparation, characterization, and electrochemical properties of electrodes using the Pattex PL50 as the binder are described. A commercial high-capacity mesocarbon microbead graphite was selected as the electrode active material. © 2015, Springer-Verlag Berlin Heidelberg. more...

Sodium iron (II) phosphate/iron (III) phosphate mixtures with different Fe(II)/Fe(III) ratio were synthesized. X-ray diffraction, scanning electron micrographs, and thermal analysis were employed to characterize the samples. The electrochemical properties of electrodes prepared by using the samples as the active material were evaluated in lithium cells. One of the samples was electrochemical tested in sodium cells. The cell cyclability was evaluated as a function of the discharge rate. The values of capacity and voltage were employed for the calculation of the specific discharge energy and power. © 2015 IEEE. more...

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. more...

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 more...

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. more...

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. more...

LiFePO4 was synthesized in the presence of high-surface area carbon-black. The carbon was added to the precursors before the formation of the crystalline phase. SEM micrographs confirmed that the addition of the fine carbon powder reduces the LiFePO4 grain size. The carbon is uniformly dispersed between the grains, ensuring a good electronic contact. Electrochemical tests showed that the material obtained by adding 10 wt.% of carbon gives enhanced performance in terms of improved practical capacity and charge/discharge rate. The specific capacity was seen to increase on increasing temperatures. The full capacity (170 mA h g−1) was delivered when discharging the cell at 80 °C and C/10 rate. The cyclability of the material was tested at room temperature and C/2 rate. The cell was cycled for over 230 cycles with an average specific capacity of about 95 mA h g−1. more...

Low-molecular-weight poly(ethyleneglycol) was tested as lithium-ion conductive matrix in a crystalline V2O5-based composite cathode. To assess the feasibility of this composite cathode in solid-state rechargeable batteries, the ion transport properties, the chemical stability and the electrochemical stability were evaluated. The cathode exhibited fairly good electrochemical properties at a moderately high temperature. At 338 K, a 7 Li diffusion coefficient of about 6.8×10−8 cm2 s−1 was measured. The cathode showed good thermal and electrochemical stability. Battery cells were assembled and their performance was evaluated at 338 K and at different discharge rates. About 270 mAh g−1 (corresponding to 1.8 lithium equivalents) were delivered when cycling the battery at a low discharge rate (0.04 mA cm−2, C/24). The active material utilization decreased with increasing discharge rate. About 1.0 lithium equivalents were cycled at 0.270 mA cm−2and only 0.33 at 0.480 mA cm−2. more...

A new concept is proposed to realize high performance lithium polymer batteries. The two-phase battery concept is based on the use of two polyethers of different molecular weight. A low molecular weight polyether is used in the composite cathode to assure high ionic conductivity while a high molecular weight polyether is used in the electrolyte formulation. In this work, a composite cathode based on a solid, low molecular weight poly(ethylenglycol) dimethyl ether (PEG-DME, M.W. 2000), was coupled with a solid polymer electrolyte (SPE) based on poly(ethylenoxide) (PEO, M.W. 4×10 6 ). The electrochemical stability window, evaluated by a slow sweep voltammetry, showed that the system has an anodic breakdown voltage higher than 4.0 V versus Li. The feasibility of two-phase batteries was evaluated by cycling tests. The results indicate that two-phase batteries have enhanced performance with respect to PEO based batteries. more...

Lithium metal–polymer electrolyte batteries with improved utilization of the active material at a moderate–low temperature (65°C) were realized. Low molecular weight poly(ethylene glycol) (PEG, MW=2000) was used as the lithium-ion conductive matrix in the composite cathode. The cathode active material was crystalline V 2 O 5 . A blend of poly(ethylene oxide) (PEO, MW=4×10 6 ) and PEG was used as a solid polymer electrolyte (SPE). The transport properties of the SPE were evaluated at various temperatures. A specific conductivity as high as 1.0×10 −4 S cm −1 was calculated at 45°C. The temperature dependence of the interfacial resistances between lithium/SPE and cathode material/PEG was evaluated. The lithium/SPE interfacial resistance decreases linearly with the temperature. The charge transfer resistance between the cathode material and PEG reaches a minimum at 60°C and it does not decrease with a further temperature increase. The data clearly show that the battery is able to work at a temperature as low as 60°C. The operating temperature was set at 65°C and the battery performance was evaluated at different discharge rates. An energy density of about 500 W h kg −1 and a power density of about 150 W kg −1 were achieved cycling the cell in about 3.3 h at 0.20 mA cm −2 . Prolonged cycling showed a capacity fading of about 0.45% per cycle. This value does not differ very much from the value found cycling the cell in liquid electrolyte. The fade in capacity was associated with an increase of cell resistance. The evolution of the lithium/SPE and cathode material/PEG interfaces resistances was monitored. The interfacial resistance increases with time, but its value is not so high as to explain the increase of the total resistance of the cell. Anyhow, this additional resistance could be responsible for the difference in the capacity fading when cycling the cell in polymer electrolyte instead of in liquid electrolyte. more...

The influence of conductive carbon additives on the electrochemical stability of PEO-based composite electrodes is addressed in the present work. The study was performed to explain the very poor performance of lithium metal, polymer electrolyte batteries with 4 V cathode materials. It was found that the anodic stability of the PEO-based electrolyte in contact with carbon additives is much lower than what is usually obtained by simple measurements on inert metallic electrodes. more...

A new concept is proposed to realize solid-state high-performance lithium polymer batteries in which two different polymers are used as ionically conductive matrices in the cathode and in the separator. A solid, low molecular weight poly(ethylene glycol) was used in the cathode while a blend with a higher molecular weight poly(ethylene oxide) (PEO) was used in the separator. The enhanced transport properties in the cathodic compartment allow us to discharge the battery (190 mAh g−1) at a moderate temperature (65°C) in a reasonable time (about 3.3 h). Batteries cycled at 100°C showed enhanced performance with respect to PEO-based batteries. At a power density of about 416 W kg−1, energy density as high as 460 Wh kg−1, based on the weight of the active material, was achieved in about 1 h of discharge. The work was developed within the ALPE (Advanced Lithium Polymer Electric Vehicle Battery) project, an Italian integrated project devoted to the realization of lithium polymer batteries for electric vehicle applications, in collaboration with the Osaka National Research Institute. Keywords: Poly(ethylene glycol), Composite cathodes, Polymer electrolytes, Lithium batteries more...

In the development of rechargeable lithium polymer batteries it is of paramount importance to control the passivation phenomena occurring at the lithium electrode interface. It is well estabilished that the type and the growth of the lithium passivation layer is unpredictably influenced by the presence of liquid components and/or impurities in the electrolyte. Therefore, one approach to improve the stability of the lithium interface is the use of liquid-free, highly pure electrolytes. The electrochemical properties of a composite polymer electrolyte obtained by hot pressing a mixture of polyethylene oxide (PEO), a lithium salt (lithium tetrafluoroborate, LiBF4) and a powdered ceramic additive (γ-LiAlO2), will be presented and discussed. The electrochemical characterization included the determination of the ionic conductivity, the anodic break-down voltage and, most importantly, the stability of the lithium metal electrode interface and the lithium stripping-plating process efficiency. The main feature of this dry, true solid-state electrolyte is a very good compatibility with the lithium metal electrode, demonstrated by a very high lithium cycling efficiency, which approaches a value of 99%. more...

Several types of lithium ion conducting polymer electrolytes have been synthesized by hot-pressing homogeneous mixtures of the components, namely, poly(ethylene oxide) (PEO) as the polymer matrix, lithium trifluoromethane sulfonate (LiCF{sub 3}SO{sub 3}), and lithium tetrafluoroborate (LiBF{sub 4}), respectively, as the lithium salt, and lithium gamma-aluminate {gamma}-LiAlO{sub 2}, as a ceramic filler. This preparation procedure avoids any step including liquids so that plasticizer-free, composite polymer electrolytes can be obtained. These electrolyte have enhanced electrochemical properties, such as an ionic conductivity of the order of 10{sup {minus}4} S/cm at 80--90 C and an anodic breakdown voltage higher than 4 V vs. Li. In addition, and most importantly, the combination of the dry feature of the synthesis procedure with the dispersion of the ceramic powder, concurs to provide these composite electrolytes with an exceptionally high stability with the lithium metal electrode. In fact, this electrode cycles in these dry polymer electrolytes with a very high efficiency, i.e., approaching 99%. This in turn suggests the suitability of the electrolytes for the fabrication of improved rechargeable lithium polymer batteries. more...

In this report are described the fabrication and the characterization of a lithium-metal, polymer electrolyte battery using a V 2 O 5 xerogel cathode. The system operates at moderate temperatures (80–100°C). The electrochemical characterization of separate components as well as of small scale devices is also reported. The work is focused on the determination of important `application' properties of the polymer electrolyte, i.e., the properties of the polymer electrolyte in real systems and true operating conditions. The work was developed within the ALPE (Advanced Lithium Polymer Electrolyte) project, an Italian project devoted to the realization of lithium polymer batteries for electric vehicle applications, in collaboration with the Corrosion Research Center of the University of Minnesota. more...

A fast and easy way to produce LiFePO4 starting from FePO4, used as iron and phosphorus source, is proposed. 5% hydrogen is employed as a reducing agent and various compounds containing lithium as lithiation agents. The selected lithiation agents included: LiCl, CH3COOLi, LiOH, Li2S, LiH, and Li2CO3. Solid state synthesis is used for the LiFePO 4 preparation and the so obtained materials are structurally characterized by XRD. The materials are used to fabricate composite electrode and their specific capacity is evaluated by low rate galvanostatic charge/discharge cycles (C/10 rate). Among the various lithium salts, the acetate give rise to the LiFePO4 with the best electrochemical performance. The morphology of this material is further investigated by SEM microscopy and the specific capacity is evaluated as a function of the discharge rate and the cycle number. © 2014 AIP Publishing LLC. more...

This paper reports the preparation and the characterization of composite electrodes based on TiO2 and LiFePO4. The electrodes were studied by using XRD, SEM, and charge/discharge cycles. The electrochemical tests comprised low rate cycling and cycling at different rates. The electrodes were used for the fabrication of lithium-ion batteries. Battery cells were assembled and electrochemical tested at various discharge rates to evaluate cell capacity and capacity retention as a function of the discharge rate. © 2014 IEEE. more...

In this paper a general method to obtain a mixture of a transition metal embedded in a matrix of lithium fluoride is proposed. The method consists in the reduction of the oxide of the transition metal with lithium hydride to form the correspondent transition metal and lithium oxide. This latter is then converted into lithium fluoride by solid state reaction with ammonium fluoride. In this work the proposed method was applied to iron(III) oxide to obtain a mixture of iron metal and lithium fluoride. The crystal structure and phase purity of the intermediate as well as the final product were analyzed by X-ray diffraction measurement and the crystallite dimensions evaluated by using the Scherrer's formula. The iron metal/lithium fluoride mixture was used as a conversion material and its electrochemical properties evaluated by galvanostatic charge discharge cycles, impedance spectroscopy and galvanostatic intermittent titration technique. As the conversion material is in its reduced state it can be coupled with a carbonaceous negative electrode to build a lithium ion battery, opening new perspectives for using conversion materials in lithium ion batteries technology. © 2013 Elsevier Ltd. All rights reserved. more...

In this paper, the morphology, the conformation, and the electrochemical performance of TiO2 nanotubes and LiFePO4 have been studied by using scanning electron microscope, XRD, and charge/discharge cycles. The electrochemical tests comprised low rate cycling, cycling at C rate, and cycling at different rates. This work was finalized to the fabrication of lithium-ion batteries based on the TiO2/LiFePO4 redox couple. Battery cells were assembled and electrochemical tests were performed to evaluate cell capacity, power, and energy. Further tests were carried out to evaluate the capacity retention as a function of cycle number and discharge current. © 2013 Springer-Verlag Berlin Heidelberg. more...

In the previous chapter we described the preparation of nano-crystalline LiFePO4 by heating amorphous nano-sized LiFePO4 (Prosini et al., J. Electrochem. Soc. 149:A886–A890, 2002). The crystalline phase was obtained after heating the amorphous compound in a tubular furnace at 550°C for 1 h under reducing atmosphere (Ar/H2). In this chapter, we further report on the electrochemical characterization of crystalline LiFePO4 obtained by firing the amorphous precursor at 550°C for different periods of time (Prosini et al., Electrochim. Acta 48:4205–4211, 2003). All the samples showed very good electrochemical performance in terms of energy and power density. Upon cycling a capacity fading affected the material, thus reducing the electrochemical performance. The initial fading was related to structural variations or contact losses between the conductive binder and the active material particles, resulting from volume variations during lithium extraction. The fading decreased upon cycling and after the 200th cycle the material was able to intercalate/deintercalate lithium for more than 500 cycles without further capacity decline. more...

The galvanostatic intermittent titration technique (GITT) and the impedance spectroscopy (IS) have been extensively used to calculate the lithium chemical diffusion coefficient in intercalation materials. The classical application of these techniques is related to systems in which the concentration of the intercalant changes monotonically as intercalation proceeds. Such a situation is valid only for topotactic solid-state intercalation reactions that lead to the formation of solid-solution phases. When the intercalation/de-intercalation of lithium is accompanied by strong electron–ion interactions, the intercalation proceeds following one or several reaction fronts, and leads to the co- existence of two phases (Andersson et al., Electrochem. Solid State Lett. 3, 66–68, 2000; Conway Electrochim. Acta. 38, 1249–1258, 1993). The co-existence of two phases makes the meaning of the chemical diffusion coefficient as a function of the composition unclear. In such a case, the chemical diffusion coefficient as obtained from GITT and IS measurements, may be taken as an effective measure which reflects the intensity of long- and short-range interactions between the intercalated species. The intercalation of lithium into electrode materials can be described and treated similarly to an adsorption process at the metal/solution interface (Vorotyntsev and Badiali, Electrochim. Acta. 39, 289–306, 1994) or to the charging of electronically conductive polymers (McKinnon and Haering, Modern Aspect in Electrochemistry, Plenum Press, New York, 1987). In the case of strong interactions between the intercalated species, a Frumkin-type sorption isotherm was used to describe the intercalation process and derive fundamental thermodynamic properties (Vorotyntsev and Badiali, Electrochim. Acta. 39, 289–306, 1994; Levi et al., J. Electrochem. Soc. 146, 1279–1289, 1999; Sato et al., J Power Sour 68, 674–679, 1997; Nishizawa et al., Electrochem. Solid State 1, 10–12, 1998; Barker et al., J. Power Sour 52, 185–192, 1994). In this chapter the chemical diffusion coefficient of lithium in 10 wt% carbon added LiFePO4 was calculated by using GITT and IS. The lithium insertion in LiFePO4 was treated as an insertion process with a Frumkin-type sorption isotherm (Prosini et al., Solid State Ionics 148, 45–51, 2002). A minimum in the lithium chemical diffusion coefficient (DLi) was predicted by the model for strong attractive interactions between the intercalation species and the host matrix. The DLi was measured as a function of the lithium content by using the galvanostatic intermittent titration technique (GITT). The diffusion coefficient was found to be 1.8 × 10?14 and 2.2 × 10?16 cm2 s?1 for LiFePO4 and FePO4, respectively with a minimum in correspondence of the peak of the differential capacity. The DLi has also been measured by impedance spectroscopy for various lithium contents. The calculated values are in very good agreement with the previously calculated ones. more...

To assess the origin of capacity loss observed during the first cycles, a study was conducted to evaluate the effect of carbon content in the composite cathode on the electrochemical performance of LiFePO4. Carbon is usually added into the composite cathode to increase the electronic contact between the active material and the electronic conductor. The conductivity of the composite cathode is expected to increase by incrementing the amount of carbon. On the other side Chen and Dahn (J. Electrochem. Soc. 149:A1184–A1189, 2002) showed that the presence of carbon, even below 1.0 wt%, causes a significant tap density decrease. The amount of carbon that is needed to optimize the electrode performance depends on the particle size of the active material. Depending upon the performance requirements, the particle size need not necessarily to be nanometric. Dahn concluded that it was important for the LiFePO4 producer to carefully note the effect of carbon coating on capacity, rate capability, and tap density. In order to investigate the factors affecting rate performance of LiFePO4 with a well defined grain size and to maximize the electrode performance, a series of electrodes were prepared with variable active material/carbon ratios. Undoped, nano-crystalline LiFePO4 was used to prepare composite electrodes containing 10, 15, and 20 wt% carbon. The electrodes were tested as cathodes in non-aqueous lithium cells (Zane et al., Electrochim. Acta 49:4259–4271, 2004). 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 charge transfer resistance reduction. The poor performance exhibited at very high discharge rates was related to the high value of the charge transfer resistance. For currents larger than 3C rate, a severe capacity fade affected the electrodes. It was concluded that the electronic contact at the LiFePO4/carbon interface plays a decisive role in material utilization at different discharge rates and affects the capacity fade upon cycling. 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. more...

In the previous chapter it was shown that a mixture of amorphous 3Fe2O3•2P2O5·10H2O, prepared by air oxidation of iron(II)phosphate, exhibited good electrochemical properties as cathode of a lithium cell (Prosini et al., J. Electrochem. Soc. 148, A1125–A1129, 2001). However, two different types of iron were formed during the heating treatment of iron(II)phosphate, namely iron(III)phosphate and iron(III)oxide. Since the latter form is electrochemically non-active for lithium intercalation in the investigated voltage range (4.0–2.0 V) (Prosini et al., Int. J. Inorg. Mater. 2, 365–370, 2000), the electrochemical properties of such material was only due to the amorphous iron(III)phosphate phase. For this reason we investigated a new synthetic route to prepare pure amorphous iron(III)phosphate. The new route involved the spontaneous precipitation from equimolar aqueous solutions of Fe(NH4)2(SO4)2·6H2O and NH4H2PO4, using hydrogen peroxide as an oxidizing agent. The material was characterized by chemical analysis, TG/DTA, XRD, and SEM. The material was tested as a cathode in non-aqueous lithium cells. Galvanostatic intermittent titration technique (GITT) was used to follow the lithium intercalation process. To evaluate the effect of firing on the specific capacity the material was heated at various temperatures up to 650°C. The material heated at 400°C showed the best electrochemical performance, delivering about 108 Ah kg?1 when cycled at 170 A kg?1 rate. The capacity fade upon cycling was found as low as 0.075% per cycle. more...