Search

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

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

This 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.