Search

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.

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.

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.

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.

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.