Showing papers in "Electrochemical and Solid State Letters in 2002"
TL;DR: In this paper, the authors describe the synthesis and properties of a kinetically improved cathode material, which is based on a critical step involving the dispersion of metal at a very low concentration (1 wt %).
Abstract: This paper describes the synthesis and the properties of a kinetically improved cathode material. The novel aspect of the synthesis is based on a critical step involving the dispersion of metal (e.g., copper or silver) at a very low concentration (1 wt %). This metal addition does not affect the structure of the cathode but considerably improves its kinetics in terms of capacity delivery and cycle life. Such an enhancement of the electrochemical properties has been ascribed to a reduction of the particle size and to an increase of the bulk intra- and interparticle electronic conductivity of both effects being promoted by the finely dispersed metal powders. This improved conductivity favors the response of thus substantiating its interest as new cathode for advanced lithium ion batteries. © 2002 The Electrochemical Society. All rights reserved.
550 citations
TL;DR: In this article, the authors used a synthetic method to extract and insert lithium into olivine at 4.1 V vs. 4.5 V and achieved an overall reversible capacity of 140 mAh/g at room temperature.
Abstract: Olivine has been produced using a new synthetic method. Reversible extraction and insertion of lithium into olivine at 4.1 V vs. lithium demonstrated that this material is a promising candidate for the cathode in lithium-ion batteries. When charged to 4.5 V, ca. 0.94 Li per formula unit can be extracted during the first charge. When charged to 4.8 V, 152 mAh/g was delivered in the first discharge. An overall reversible capacity of 140 mAh/g has been attained at room temperature. A flat two-phase region with open-circuit voltage V was identified. The thermal stability of the charged cathode was evaluated by thermogravimetric analysis and differential scanning calorimetry. © 2002 The Electrochemical Society. All rights reserved.
402 citations
TL;DR: In this paper, a chelated borate anion, BOB [bis(oxalato)borate] is evaluated as the electrolyte solute for lithium-ion cells by both electrochemical means and cell testing.
Abstract: A new lithium salt based on a chelated borate anion, BOB [bis(oxalato)borate] is evaluated as the electrolyte solute for lithium-ion cells by both electrochemical means and cell testing. Controlled potential coulometry study reveals that the anion can stabilize aluminum substrate to more positive potentials than the popular hexafluorophosphate anion does, while slow scan cyclic voltammograms show good compatibility of the salt with graphitizable carbonaceous anode as well as satisfactory stability against charged cathode surface. The lithium-ion cells containing this salt as electrolyte solute exhibit excellent capacity utilization, capacity retention as well as rate capability at room temperature. Probably due to the fact that the new anion contains no labile fluorine and is thermally stable, electrolyte solutions based on it demonstrate stable performance in cells even at 60°C, where -based electrolytes would usually fail. The preliminary results reported herein provide a possible solution to the instability of the Li-ion cell performance at the elevated temperatures anticipated for heavy duty applications such as electric or hybrid electric vehicle missions. © 2001 The Electrochemical Society. All rights reserved.
371 citations
TL;DR: LiFePO4 powders were synthesized under two different conditions ~hydrothermal or mechanochemical activation! using iron~II! phosphate and lithium phosphate as starting materials as mentioned in this paper.
Abstract: LiFePO4 powders were synthesized under two different conditions ~hydrothermal or mechanochemical activation! using iron~II! phosphate and lithium phosphate as starting materials. The samples were characterized by X-ray diffraction, chemical titration, and their electrochemical performance was investigated in terms of cycling behavior and impedance response. We also report the benefit of introducing an electronic conductor precursor ~typically a sucrose! during or after the synthesis to overcome the poor charge transfer associated to the lithium iron phosphate.
292 citations
TL;DR: In this article, the authors showed that the lattice of coated LiCoO 2 expands and contracts in exactly the same way as uncoated Li x CoO 2 during charge and discharge.
Abstract: Recently, Cho et al. studied the effects of a ZrO 2 coating on the electrochemical behavior of Li/Li x CoO 2 cells. They found that the capacity retention to 4.4 V was significantly improved for cells having electrodes incorporating coated material compared to those with uncoated LiCoO 2 . They suggested that the thin coating suppressed the lattice expansion of Li x CoO 2 during cycling, leading to improved behavior. Our results on LiCoO 2 coated with ZrO 2 , reported here, confirm the improved cycling behavior. X-ray diffraction (XRD) patterns collected with long counting times show that the coated material is nanocrystalline ZrO 2 . In situ XRD results indicate that the lattice of coated Li x CoO 2 expands and contracts in exactly the same way as uncoated Li x CoO 2 during charge and discharge. These results prove that the ZrO 2 coating does not affect the lattice expansion of LiCoO 2 , in contrast to the results reported by Cho et al. We believe that the improved cycling behavior is caused by a reduction in the contact area between LiCoO 2 and electrolyte.
285 citations
TL;DR: In this paper, a hybrid capacitor in neutral KCl aqueous electrolyte, which consists of amorphous manganese oxide (a-MnO 2.nH 2 O) as a cathode and activated carbon as an anode, was reported.
Abstract: This study reports a hybrid capacitor in neutral KCI aqueous electrolyte, which consists of amorphous manganese oxide (a-MnO 2 .nH 2 O) as a cathode and activated carbon as an anode. The electrochemical performance of the hybrid capacitor is characterized by cyclic voltammetry and a dc charge/discharge test. The hybrid capacitor shows ideal capacitor behavior with an extended operating voltage of 2 V. The extended operating voltage is preferentially attributed to having asymmetric electrodes with different stable voltage windows and good electrochemical stability in neutral KCl aqueous electrolyte. According to the extended operating voltage, the energy density of the hybrid capacitor at a current density of 0.25 A/g, was found to be 28.8 Wh/kg which is comparable to that of an amorphous ruthenium oxide capacitor (26.7 Wh/kg). The hybrid capacitor also shows no degradation of capacitance during 100 cycles except an initial loss of 7% within a few cycles.
260 citations
TL;DR: ZnO-coated LiNi 0. 5 Mn 1. 5 O 4 powders with excellent electrochemical cyclability and structural stability at elevated temperature have been synthesized by a sol-gel method as mentioned in this paper.
Abstract: ZnO-coated LiNi 0 . 5 Mn 1 . 5 O 4 powders with excellent electrochemical cyclability and structural stability at elevated temperature have been synthesized by a sol-gel method. The structural degradation of the as-preparedLiNi 0 . 5 Mn 1 . 5 O 4 and ZnO-coated LiNi 0 . 5 Mn 1 . 5 O 4 electrodes before and after cycling in the 5 V region has been studied. The ZnO-coated LiNi 0 . 5 Mn 1 . 5 O 4 electrode showed almost no capacity loss and retained its original cubic spinel structure after 50 cycles. We found that ZnO played an important role in reducing the HF content in the electrolyte solution.
241 citations
TL;DR: In this article, the authors report live observations of lithium polymer batteries upon cycling within the microscope antechamber by means of a scanning electron microscope, equipped with a transfer system that avoids sample air exposure.
Abstract: We report live observations of lithium polymer batteries upon cycling within the microscope antechamber by means of a scanning electron microscope, equipped with a transfer system that avoids sample air exposure. The well-established direct correlation between current density and dendrite formation is confirmed, and the formation of a mossy or dendritic interface was evidenced to be at the origin of the delaminating between the substrate, where the lithium is plated, and the polymer. These experiments enable a better understanding of the dendrite formation mechanism, like the important finding that they grow tipwise as well as sidewise. © 2002 The Electrochemical Society. All rights reserved.
222 citations
TL;DR: In this article, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12, for the LPI-ARTICLE-2002-023.
Abstract: Reference LPI-ARTICLE-2002-023doi:10.1149/1.1432783View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
220 citations
TL;DR: In this paper, the properties of monoclinic lithium vanadium phosphate Li 3 V 2 (PO 4 ) 3 were investigated using X-ray diffraction (XRD) and electrochemical methods.
Abstract: The properties of the monoclinic lithium vanadium phosphate Li 3 V 2 (PO 4 ) 3 are investigated using X-ray diffraction (XRD) and electrochemical methods. Electrochemical measurements conducted in half-cells with Li 3 V 2 (PO 4 ) 3 as the cathode material and lithium metal as the anode have shown that this material exhibits an excellent reversibility when the charge extracted is confined to that equivalent to two lithiums per formula unit. The extraction of the last lithium is observed at a potential greater than 4.6 V vs. Li/Li + and involves a significant overvoltage. Upon discharge, however, XRD has shown that the original structure is recovered.
218 citations
TL;DR: In this paper, the authors demonstrate that the stability of Li(Ni,Mn)O 2 materials is due to the particular valence distribution on the transition metals in this material.
Abstract: Li(Ni,Mn)O 2 materials have recently shown promise as high capacity stable electrodes for advanced rechargeable lithium batteries. Using first principles quantum mechanical energy computations we demonstrate that the stability of these materials is due to the particular valence distribution on the transition metals in this material. Spin density calculations indicate that the Mn ion has oxidation state +4 independently of the Li content in the material, while Ni is oxidized from Ni 2 + to Ni 4 + upon removing Li. The high insertion voltage for the LiNi 0 . 5 Mn 0 . 5 O 2 can be partly attributed to the change in Mn-Ni interaction upon Li cycling.
TL;DR: In this paper, a hybrid type pseudocapacitor/electric double layer capacitor (EDLC) was investigated and its electrochemical properties were investigated, and stable charge/discharge behaviors were observed with much higher specific capacitance values of 530 F/g compared with that of EDLC.
Abstract: In order to enhance energy density, a hybrid type pseudocapacitor/electric double layer capacitor (EDLC) was considered and its electrochemical properties were investigated. At various current densities, stable charge/discharge behaviors were observed with much higher specific capacitance values of 530 F/g compared with that of EDLC (230 F/g), by introducing as a cathode material. By using the modified cathode of a /activated carbon composite electrode, the specific capacitance was less sensitive to charge/discharge current density exhibiting stable power characteristics. © 2001 The Electrochemical Society. All rights reserved.
TL;DR: In this article, LiBOB is shown to stabilize graphitic anode materials in neat propylene carbonate (PC) while supporting reversible lithium ion intercalation/deintercalation, a unique behavior hitherto unobserved for any electrolyte salts.
Abstract: This paper summarizes the preliminary results of our recent finding that lithium bis(oxalato)borate (LiBOB) can effectively stabilize graphitic anode materials in neat propylene carbonate (PC) while supporting reversible lithium ion intercalation/deintercalation, a unique behavior hitherto unobserved for any electrolyte salts. This ability of LiBOB to protect graphite from exfoliation in PC offers unprecedented flexibility for the efforts of reformulating lithium-ion electrolytes, where the displacement of the high melting solvent component ethylene carbonate by PC is no longer restricted by the concern of PC instability on graphitic anode surface. © 2002 The Electrochemical Society. All rights reserved.
TL;DR: In this paper, three cathode compositions (La0.8Sr0.2FeO3d, La0.7Sr 0.3Fe0.4O3-d) have been tested as SOFC cathodes at operating temperatures from 650 degrees C to 750 degrees C.
Abstract: Three cathode compositions (La0.8Sr0.2FeO3-d, La0.7Sr0.3Fe0.8Ni0.2O3-d and LaNi0.6Fe0.4O3-d) have been tested as SOFC cathodes at operating temperatures from 650 degrees C to 750 degrees C. Sintering temperatures were established for each cathode composition to provide optimized cell performance. La0.8Sr0.2FeO3-d exhibited the highest power density (> 900 mW/cm2 at 750 degrees C and 0.7 V), and indicated excellent performance stability over a 300 hour period.
TL;DR: In situ X-ray absorption spectroscopy (XAS) of the Mn and Ni K-edges and 6 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) was carried out during the first charging and discharging process for the layered LiNi 0.5 Mn 0. 5 O 2 cathode material as discussed by the authors.
Abstract: In situ X-ray absorption spectroscopy (XAS) of the Mn and Ni K-edges and 6 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy have been carried out during the first charging and discharging process for the layered LiNi 0 . 5 Mn 0 . 5 O 2 cathode material. The Ni K-edge structure in the X-ray absorption near-edge structure (XANES) spectrum exhibits a rigid positive energy shift with increased Li deintercalation level, while the Mn XANES spectra do not show any substantial energy changes. The Ni edge shifts back reversibly during discharge. Further Li-ion intercalation at ∼1 V (vs. Li) could be accomplished by reduction of the Mn 4 + ions. The 6 Li MAS NMR results showed the presence of Li in the Ni 2 + /Mn 4 + layers, in addition to the expected sites for Li in the lithium layers. All the Li ions in the transition metal layers are removed on the first charge, leaving residual lithium ions in the lithium layers.
TL;DR: In this paper, a solid oxide fuel cell (SOFC) anode material designed for use with C-containing fuels is presented, which is a composite of an electronically conducting ceramic, La 0.8 Sr 0. 2 Cr 0. 8 Mn 0.2 O 3 - Φ, an ionically conducting ceramic and a small fraction of Ni.
Abstract: Results are presented on a solid oxide fuel cell (SOFC) anode material designed for use with C-containing fuels: a composite of an electronically conducting ceramic, La 0 . 8 Sr 0 . 2 Cr 0 . 8 Mn 0 . 2 O 3 - Φ , an ionically conducting ceramic, Ce 0 . 9 Gd 0 . 1 O 1 . 9 5 (GDC), and a small fraction Ni. These ceramic-based anodes were tested in SOFCs with GDC bulk electrolytes. The anode performance was comparable to that for Ni-GDC anodes with hydrogen and methane fuels. The anodes also provided good performance with propane and butane and, unlike Ni-GDC, there was little or no coking. The 4 wt % Ni content in the anode was necessary to obtain good performance, indicating that a small amount of Ni provides a substantial electrocatalytic effect while not causing coking. Initial cell test results showed good cell stability and indicated that the anodes were not affected by cyclic oxidation and reduction.
TL;DR: LiMn 2 O 4 spinel oxide has been surface/chemically modified with Li x CoO 2, LiNi 0. 5 Co 0.5 O 2, Al 2 O 3, and MgO using a chemical processing procedure followed by heat-treatment at 300-800°C as mentioned in this paper.
Abstract: LiMn 2 O 4 spinel oxide has been surface/chemically modified with Li x CoO 2 , LiNi 0 . 5 Co 0 . 5 O 2 , Al 2 O 3 , and MgO using a chemical processing procedure followed by heat-treatment at 300-800°C. The surface/chemically modified samples show much better capacity retention at both 25 and 60°C than does the unmodified LiMn 2 O 4 (41% fade in 100 cycles at 60°C). Among the various compositions investigated, the LiNi 0 . 5 Co 0 . 5 O 2 -modified sample shows superior capacity retention with only 2.8% fade in 100 cycles at 60°C with around 110 mAh/g. The Al 2 O 3 -modified sample shows a higher capacity of 130 mAh/g, but with a faster fade (16% in 100 cycles at 60°C). The Li 0 . 7 5 CoO 2 -modified sample shows the best combination of capacity (124 mAh/g) and retention (8% fade in 100 cycles at 60°C). The modified samples also exhibit better capacity retention after aging at 55°C at 60-70% depth of discharge.
TL;DR: In this article, a binary hydrous oxide with an amorphous structure (denoted as a-(Co + Ni)(OH) 2.nH 2 O) anodically deposited from a CoCl 2.6H 2O + NiCl 2.6H2O solution with its Co:Ni ratio of 4:6 and pH 8.0 exhibited a very large pseudocapacitance of ca. 730 F g -in 1 M NaOH.
Abstract: Binary hydrous cobalt-nickel oxide with an amorphous structure (denoted as a-(Co + Ni)(OH) 2 .nH 2 O) anodically deposited from a CoCl 2 .6H 2 O + NiCl 2 .6H 2 O solution with its Co:Ni ratio of 4:6 and pH 8.0 exhibited a very large pseudocapacitance of ca. 730 F g - in 1 M NaOH. The electrochemical reversibility of this material was examined at various charging-discharging currents in 1 M NaOH with different temperatures. This binary hydrous oxide exhibiting ideally pseudocapacitive behavior (i.e., high reversibility, high specific capacitance, and high power property) has been demonstrated to be a potential candidate for the application of electrochemical supercapacitors. The morphology and rough nature of this deposit were demonstrated through means of atomic force microscopy.
TL;DR: In this article, the formation of a solid electrolyte interface on LiNi 0. 8 5 Co 0. 1 5 O 2 cathodes from lithium-ion cells cycled at 40 and 70°C was observed and characterized using soft X-ray absorption spectroscopy (XAS).
Abstract: The formation of a solid electrolyte interface (SEI) on LiNi 0 . 8 5 Co 0 . 1 5 O 2 cathodes from lithium-ion cells cycled at 40 and 70°C was observed and characterized using soft X-ray absorption spectroscopy (XAS). XAS measurements were made in the energy region between 500 and 950 eV, encompassing the Ni and Co L 3 - and L 2 -edges and at the K-edges of O and F. Measurements, obtained in the total electron yield mode, are surface sensitive, probing to a depth of ∼5 nm. XAS at the F K-edge demonstrates the presence of poly(vinylidene fluoride) (PVdF) in addition to LiF on the surface of cycled electrodes. The results indicate that the PVdF in the cycled electrodes is largely intact and that the LiF comes from decomposition of LiPF 6 from the electrolyte. XAS also suggests Fe contamination of cycled cathodes.
TL;DR: In this paper, a LiCoPO 4 cathode material with the highest discharge capacity (125 mAh/g) is reported, which is obtained by using a novel solid-state synthesis procedure, using an alternative cobalt-containing precursor (CoNH 4 PO 4 ) and a lithium excess synthesis with carbon black as temporal dispersing agent, later eliminated as CO 2.
Abstract: A LiCoPO 4 cathode material with, to our knowledge the highest discharge capacity (125 mAh/g) is reported. The phosphate is obtained by using a novel solid-state synthesis procedure. The basic idea of the novel synthesis procedure is the use of an alternative cobalt-containing precursor (CoNH 4 PO 4 ) and a lithium excess synthesis with carbon black as temporal dispersing agent, later eliminated as CO 2 . The carbon black addition produces lower average particle size than conventional preparations, yielding a finely dispersed solid. The low particle size is responsible for a better electrochemical behavior. Finally the effects of scan rate and potential window on the electrochemical performance are discussed.
TL;DR: In this paper, the electrochemical performance of 3D metal oxide (MO) electrode materials for Li-ion batteries was studied in the form of Li/CoO(Co 3 O 4 ) half-cells.
Abstract: The electrochemical performance of 3d metal oxide (MO) electrode materials for Li-ion batteries was studied in the form of Li/CoO(Co 3 O 4 ) half-cells. Reversible capacity in the 750-1000 mAh/g range was achieved and sustained over numerous charge-discharge cycles both at room temperature and at 55°C. The studied oxides were then used as negative-electrode active materials to assemble larger plastic MO/LiCoO 2 Li-ion cells, which exhibited an average output voltage of 2 V and a stable reversible specific energy of 120 Wh/kg during extended cycling at ambient and elevated temperatures. This value can be compared to 180 Wh/kg obtained for similar C/LiCoO 2 Li-ion cells. Based on modeling, several scenarios involving material considerations present the optimum method for boosting the energy density of such MO/LiCoO 2 Li-ion systems.
TL;DR: In this paper, a ceria-based electrolyte with different noble metals-containing anode at 600°C was used for the promotion of direct electrochemical oxidation of hydrocarbons in a solid oxide fuel cell.
Abstract: The promotion of direct electrochemical oxidation of hydrocarbons in a solid oxide fuel cell was investigated using a ceria-based electrolyte with different noble metals-containing anode at 600°C. The objective was to avoid interference from a large amount of steam and CO 2 being produced by discharging the cell, because these gases degrade the anode performance, especially at a high fuel utilization. Ru was an effective catalyst for removing these gases from the anode surface due to its high catalytic activity for the steam and CO 2 reforming of hydrocarbons. The resulting peak power densities reached 750 mW cm - 2 with dry methane, which was comparable to the peak power density of 769 mW cm - 2 with wet (2.9 vol %H 2 O) hydrogen. The cell performance was maintained at a high level regardless of the change in methane utilization from 12 to 46% but was significantly reduced by increasing hydrogen utilization from 13 to 42%. The anodic reaction of hydrogen was controlled by the slow surface diffusion of hydrogen, while the anodic reaction of methane was not subject to the onset of such a gas-diffusion process.
TL;DR: In this paper, a bottom-up deposition in 200 nm trenches by an acid-copper sulfate with only two additives [poly(ethylene glycol) (PEG) and Cl ] is achieved.
Abstract: Copper bottom-up deposition in 200 nm trenches by an acid-copper sulfate with only two additives [poly(ethylene glycol) (PEG) and Cl ] is achieved. The inhibiting effect of electrodeposition by PEG is strongly related to Cl - concentration. Secondary-ion mass spectroscopy measurements show that Cl - is consumed in the electroplating process. The explanation of bottom-up deposition realized in copper superfilling, in which the decrease of Cl - concentration causes rapid electrodeposition on trench bottoms, is verified experimentally.
TL;DR: In this article, a method for determination of Young's modulus (E) of thin porous films using data obtained by ellipsometric porosimetry (EP) is reported.
Abstract: A method for determination of Young's modulus (E) of thin porous films using data obtained by ellipsometric porosimetry (EP) is reported. The calculated E values are in good agreement with data obtained by nondestructive methods like surface acoustic wave spectroscopy (SAWS) and Brillouin light scattering (BLS). These three methods (SAWS, BLS, and EP) use different physical ideas for determination of Young's modulus. Good agreement among these data suggests that the obtained data are more realistic than data obtained by nanoindentation that gives remarkably larger E values. © 2002 The Electrochemical Society. All rights reserved.
TL;DR: Ionic liquids, 1-ethyl-3-methylimidazolium hexafluorotantalate (EMITaF 6 ) and hexacrylamide hexaflamide (EMINbF 6 ), were synthesized by a new method.
Abstract: Ionic liquids, 1-ethyl-3-methylimidazolium hexafluorotantalate (EMITaF 6 ) and hexafluoroniobate (EMINbF 6 ) were synthesized by a new method. They showed lower melting points and higher decomposition temperatures than popular EMIBF 4 due to larger anion size. Electrolytic conductivities of these ionic liquids were about 6 mS cm - 1 at 25°C. Lowering the melting point of ionic liquids did not result in the improvement of low-temperature characteristics of carbon double-layer capacitors, however, the new ionic liquids showed long life compared with EMICF 3 SO 3 , EMI(CF 3 SO 2 ) 2 N, and EMI(C 2 F 5 SO 2 ) 2 N at 3.0 V, 70°C. The derivatives of the new ionic liquids having a methyl group in 2-position (l-ethyl-2,3-dimethylimidazolium salts) were not ionic liquids at room temperature.
TL;DR: In this paper, the possibility of using a strong anion coordinate agent, tris(pentafluorophenyl) borane (TPFPB), to suppress the thermal decomposition of LiPF 6 -based electrolyte was studied.
Abstract: The possibility of using a strong anion coordinate agent, tris(pentafluorophenyl) borane (TPFPB), to suppress the thermal decomposition of LiPF 6 -based electrolyte was studied. Cyclic voltammogram measurements showed thataddition of 0.1 M TPFPB maintained electrochemical stability of a LiPF 6 -based electrolyte at 55°C for a week, while under the same conditions severe degradation in electrochemical stability was observed in the same LiPF 6 -based electrolyte without the TPFPB additive. A Li/LiMn 2 O 4 cell with a composite LiPF 6 -based electrolyte containing 0.1 M TPFPB additive also exhibited superior capacity retention and cycling efficiency at 55°C than a cell with an electrolyte without additive. These data demonstrate the excellent effect of TPFPB additive in improving the thermal stability of LiPF 6 -based electrolyte.
TL;DR: In this article, a molecular junction formed by a 10-15 A organic monolayer between carbon and mercury contacts exhibited conductance switching for several polygonal structures, including a terphenyl junction and a planar quinoid structure.
Abstract: A molecular junction formed by a 10-15 A organic monolayer between carbon and mercury contacts exhibited conductance switching for several monolayer structures. When the carbon potential was scanned to a sufficiently negative voltage relative to the mercury, the junction resistance suddenly decreased by at least an order of magnitude, and high resistance could be restored by a positive voltage scan. The high and low conductance states were persistent, and conductance switching was repeatable at least 100 cycles for the case of a terphenyl junction. The switching behavior is consistent with phenyl ring rotation and formation of a planar, quinoid structure as a consequence of electron injection into the monolayer. A unique feature of the junction structure is the strong electronic coupling between the monolayer p system and the graphitic carbon through a quinoid double bond. Not only does this interaction lead to high conductivity and possible practical applications as a molecular switch, it also combines the electronic properties of the conjugated monolayer with those of the graphitic substrate. The switching mechanism reported here is an example of ‘‘dry electrochemistry’’ in which a redox process appears to occur under the influence of a high electric field in the absence of solvent or electrolyte. © 2002 The Electrochemical Society. @DOI: 10.1149/1.1490716#
TL;DR: In this article, a thin film of elementary nickel was formed by atomic layer deposition (ALD), which consisted of two consecutive chemical reaction steps: an oxidizing step and a reducing step.
Abstract: A thin film of elementary nickel was formed by atomic layer deposition (ALD). The deposition cycle consisted of two consecutive chemical reaction steps: an oxidizing step and a reducing step. An atomic layer of nickel oxide was made by sequentially supplying bis(cyclopentadienyl)-nickel as a nickel precursor and water as an oxidation agent; the preformed atomic layer of nickel oxide was then reduced to elementary nickel metal by exposure to hydrogen radical at a deposition temperature of 165°C. Auger electron spectroscopy analysis detected negligible oxygen content in the grown films, indicating that the hydrogen radical had completely reduced the nickel oxide to a metallic thin film. In addition, carbon impurities in the film dropped from 16 atom % to less than 5 atom % during the reduction reaction. The proposed two-step ALD method for elementary metals was successful in forming continuous and conformal nickel thin films. These nickel films formed an effective glue layer between chemical vapor deposited copper and a diffusion barrier layer of TiN. The adhesion of a 1 μm thick copper film to a 15 nm thick nickel glue layer over a TiN barrier film was excellent, with no failures occurring during adhesive tape peel tests. © 2002 The Electrochemical Society. All rights reserved.
TL;DR: In this article, the capacity retention behavior of LiMn 2 O 4 and the cation-substituted L 2 - y M y O 4 spinel oxides has been analyzed.
Abstract: With an objective of understanding the differences in the capacity retention behavior of LiMn 2 O 4 and the cation-substituted LiMn 2 - y M y O 4 (M = Li, Co. and Ni) spinel oxides, the peak broadening in the X-ray diffraction patterns on extracting lithium has been analyzed. An analysis of the LiMn 2 O 4 and LiMn 2 - y M y O 4 samples before and after treating at room temperature with acid or an oxidizing agent (NO 2 BF 4 ) or at 55°C with electrolyte reveals that the LiMn 2 O 4 system experiences a larger amount of microstrain during these treatments (lithium extraction) compared to the LiMn 2 - y M y O 4 systems. Additionally, the two cubic phases formed at lower lithium contents have a larger difference in lattice parameters in Li 1 - x Mn 2 O 4 compared to Li 1 - x Mn 2 - y M y O 4 . The observation of nearly the same amount of manganese dissolution in LiMn 2 O 4 and LiMn 2 - y M y O 4 suggests that the faster capacity fade in the former is due to the development of microstrain and the larger difference in lattice parameters between the two cubic phases.
TL;DR: Li 2 O/M and Li 2 S/M (M = Co, Fe) composites that contain electrochemically active lithium were made by ballmilling Li 2 O with metal powder as discussed by the authors.
Abstract: This paper demonstrates Li 2 O/M and Li 2 S/M (M = Co, Fe) composites that contain electrochemically active lithium. The composites were made by ballmilling Li 2 O or Li 2 S with metal powder. The resulting materials had average grain sizes of ∼100 A and enormous reversible capacities of up to 600 mAh/g. When cycled within appropriate voltage limits, the electrodes showed no capacity fading. These composites are compatible with lithium-ion technology and could provide a safe, high-energy density alternative to conventional intercalation electrodes.