Results 1 - 10 of 11
Results 1 - 10 of 11. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] Lithium batteries are characterized by high specific energy, high efficiency and long life. These unique properties have made lithium batteries the power sources of choice for the consumer electronics market with a production of the order of billions of units per year. These batteries are also expected to find a prominent role as ideal electrochemical storage systems in renewable energy plants, as well as power systems for sustainable vehicles, such as hybrid and electric vehicles. However, scaling up the lithium battery technology for these applications is still problematic since issues such as safety, costs, wide operational temperature and materials availability, are still to be resolved. This review focuses first on the present status of lithium battery technology, then on its near future development and finally it examines important new directions aimed at achieving quantum jumps in energy and power content. (author)
[en] Highlights: ► A nanostructured tin–carbon anode is obtained by high energy mechanical milling. ► The electrode shows enhanced electrochemical performance in lithium cell. ► The nanostructured electrode has capacity ranging from 400 to 500 mAh g−1. ► The electrode is used in a lithium ion cell with a LiNi0.5Mn1.5O4 cathode. ► The 4.3 V-cell has capacity of 120 mAh g−1 and energy of 520 Wh kg−1 vs. cathode. -- Abstract: A tin–carbon composite synthesized by high energy mechanical milling (HEMM) technique is characterized here as an anode material for lithium ion battery. The composite morphology and structure are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively, and its electrochemical behavior is characterized by cyclic voltammetry (CV) and galvanostatic cycling in lithium cell. The electrode evidences highly nanostructured morphology and enhanced lithium–tin alloying–de-alloying process stability as the mechanical milling time is increased, with capacity ranging from 500 to 400 mAh g−1. Further important characteristic of the tin–carbon nanostructure reported here is the very high rate capability, extending up to 2 A g−1, that finally allows to its application in a high voltage, high rate lithium ion cell using the LiNi0.5Mn1.5O4 spinel cathode. The cell shows a working voltage of 4.3 V and a capacity of 120 mAh g−1 obtained at 1 C rate. The very promising features of the cell, its high energy and power density, and the low cost of the involved materials, suggest that the electrode reported here can be efficiently used as an anode in advanced configuration lithium ion battery
[en] A tin antimony based electrode has been synthesized in the form of nanometric particles housed into the pores of a protective, amorphous carbon matrix. Electrochemical results, obtained using this material as the working electrode in a lithium cell, suggested that the electrochemical process involves both SnSb intermetallic and Sn metal, present in the carbon matrix. Moreover, the results demonstrated that the optimized nanostructure prevents the mechanical drawbacks, associated with the volume changes during the alloying processes, which normally affect this class of materials. Finally, a lithium ion battery based on the SnSb-C electrode as the anode and lithium iron phosphate, LiFePO4, as the cathode, showed very promising performance.
[en] In this work we evaluate the safety characteristics of an advanced Sn-C/EC:PC 1:1, LiPF6 PVdF gel electrolyte (GPE)/LiNi0.5Mn1.5O4 lithium ion polymer battery. The tests are performed by using a complex analysis that combines Differential Scanning Calorimetry (DSC) Thermal Gravimetric Analysis (TGA), and Mass Spectrometry (MS). This is a very convenient tool since it detects eventual thermal decomposition processes and provides information on the nature of their products. The results of the DSC-TGA-MS analysis are here reported and discussed. They demonstrate that both the anode and the cathode sides of the battery may stand temperatures up to ca. 200 deg. C without undergoing thermal decomposition. This is a convincing evidence that the Sn-C/LiNi0.5Mn1.5O4 lithium ion polymer battery is safe.
[en] Several gel membranes of the type PVdF/EC-PC/SiO2 without and with electrolyte salts have been characterised by vibrational spectroscopy and by galvanostatic cycling tests. It is found that the structure of the PVdF matrix in the membranes depends on the gel composition and preparation conditions. At high loads of polymer parts of the PVdF chains assume a TGTG' conformation typical of the so-called 'structural form II'. The formation of PVdF of form II is favoured when slow cooling rates are employed during the membrane preparation. In galvanostatic cycling tests in combination with a Sn/SnSb electrode, the present gel-type polymer electrolytes give results comparable to those obtained with the corresponding liquid electrolytes
[en] Iron oxide nanostructures, a promising alternative to carbon-based anode in lithium-ion batteries, can be produced using a hard template route. This procedure guarantees the formation of Fe2O3 nanowires with comparable diameter and size (average diameter 8 nm) with a dominant cubic γ-phase at the surface. Lithium exposure of the iron oxide nanowires in ultra-high-vacuum (UHV) conditions induces reduction of the Fe ion, leading to a Fe3O4 and then to a Fe2+ phase, as determined by means of core-level photoemission spectroscopy. Mild annealing of Fe2O3 in UHV determines an oxygen content reduction for the nanowires at lower temperature with respect to the bulk phase. The morphology and the evolution of the electronic properties upon reduction have been compared to those of micro-sized bulk-like grains, to unravel the role of the reduced size and surface-volume ratio
[en] In this work the synthesis of a nickel doped cubic manganese spinel has been studied for application as cathode material in secondary lithium batteries. Six different experimental approaches have been tested in order to carry out a screening of the various possible synthetic routes. The used synthetic strategies were wet chemistry (WC), solid state (SS), combustion synthesis (CS), cellulose-based sol-gel synthesis (SG-C), ascorbic acid-based sol-gel synthesis (SG-AA) and resorcinol/formaldehyde-based sol-gel synthesis (SG-RF). The goal of our study is to obtain insights about how the synthesis conditions can be modified in order to achieve a material with improved electrochemical performances in such devices, especially in high current operating regimes. The synthesized materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), atomic absorption, inductively coupled plasma (ICP-MS) atomic emission spectroscopy, surface area measurements and tested as high voltage cathodes in Li-ion electrochemical devices.
[en] Highlights: → 1-Butyl-1-methylpyrrolidinium hexafluorophosphate was used as a flame-retarding additive. → An addition of BMP-PF6 suppressed the flammability and improved the thermal stability. → The optimum BMP-PF6 content in the electrolyte was found to be 10 wt.%. - Abstract: 1-Butyl-1-methylpyrrolidinium hexafluorophosphate (BMP-PF6) was used as a flame-retarding additive in the liquid electrolyte, and the influence of BMP-PF6 content on cycling performance and thermal properties of lithium-ion batteries was investigated. Self-extinguishing time and DSC studies demonstrated that the addition of BMP-PF6 to the electrolyte provided a significant suppression in the flammability of the electrolyte and an improvement in the thermal stability of the cell. The optimum BMP-PF6 content in the electrolyte was found to be 10 wt.% for improving safety without degrading cycling performance of the cell.
[en] Highlights: • A quaternary PEC-LiTFSI-Pyr_1_4TFSI-Silica fiber electrolyte was prepared by a solvent casting method. • Both electrochemical and mechanical properties were improved by the presence of the Silica fiber. • The electrolyte showed a t_L_i_+ value of 0.36 with an anodic stability extended up to 4.5 V vs. Li/Li"+. • A prototype Li/LiFePO_4 polymer cell delivered a discharge capacity of about 100 mAh g"−"1 (75 °C, C/15). - Abstract: Poly(ethylene carbonate) (PEC) is known as an alternating copolymer derived from carbon dioxide (CO_2) and an epoxide as monomers. Here, we describe a new quaternary PEC-based composite electrolyte containing lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt, N-n-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (Pyr_1_4TFSI) ionic liquid, and an electrospun silica (SiO_2) fiber (SiF) with a submicron diameter in view of its possible applications in solid-state Li polymer batteries. A free-standing electrolyte membrane is prepared by a solvent casting method. The Pyr_1_4TFSI ionic liquid enhances the ionic conductivity of the electrolyte as a result of its plasticizing effect. The electrochemical properties, such as ionic conductivity and Li transference number (t_L_i_+), as well as mechanical strength of the electrolyte, are further improved by the SiF. We show that the quaternary electrolyte has a conductivity of the order of 10"−"7 S cm"−"1 at ambient temperature and a high t_L_i_+ value of 0.36 with an excellent flexibility. A prototype Li polymer cell using LiFePO_4 as a cathode material is assembled and tested. We demonstrate that this battery delivers a reversible charge-discharge capacity close to 100 mAh g"−"1 at 75 °C and C/15 rate. We believe that this work may pave the road to utilize CO_2 as a carbon source for highly-demanded, functional battery materials in future
[en] XRD, Sem micrographs, Bet analyses and typical electrochemical experiments (cyclic voltammetry, step voltammetry and Li insertion/de insertion at constant current) have been carried out to characterize a new type of soft carbons obtained by pyrolysis of hexa phenylbenzene (Hb). By means of XRD and cyclic voltammetry at least three different type of sites for lithium storage were found. The first is graphite like type with d 002 graph ene layer distance greater than pure graphite; the second is associated to disordered volumes among crystallities and the third is represented by Li sites at the hydrogen-terminated edges of hexagonal carbon fragments, characterized by higher energy in comparison with simple insertion sites. These last two types of sites are able to store some extra lithium, compared to pure graphite. BET analyses and cyclic voltammetries demonstrate the key role of the milling time on the characteristics and properties of this HPB pyrolysed carbon. Specific capacities shown by this pyrolysed material in Li coin-type cell have been also reported