Showing papers in "Electrochemical and Solid State Letters in 2003"
TL;DR: In this article, anode materials of nanostructured silicon have been prepared by physical vapor deposition and characterized using electrochemical methods, and electrodes were prepared in thin-film form as nanocrystalline particles (12 nm mean diameter) and as continuous amorphous thin films (100 nm thick).
Abstract: Anode materials of nanostructured silicon have been prepared by physical vapor deposition and characterized using electrochemical methods. The electrodes were prepared in thin-film form as nanocrystalline particles (12 nm mean diameter) and as continuous amorphous thin films (100 nm thick). The nanocrystalline silicon exhibited specific capacities of around 1100 mAh/g with a 50% capacity retention after 50 cycles. The amorphous thin-film electrodes exhibited initial capacities of 3500 mAh/g with a stable capacity of 2000 mAh/g over 50 cycles. We suggest that the nanoscale dimensions of the silicon circumvents conventional mechanisms of mechanical deterioration, permitting good cycle life.
691 citations
TL;DR: The formation of porous on titanium was investigated in electrolytes containing low concentrations of HF (0.05-0.4 wt %) under optimized electrolyte conditions and extended polarization as mentioned in this paper.
Abstract: The formation of porous on titanium was investigated in electrolytes containing low concentrations of HF (0.05-0.4 wt %). Under optimized electrolyte conditions and extended polarization, highly ordered porous is obtained that consists of pore arrays with single pore diameter of 140 nm and a pore spacing of 150 nm. During the formation process, significant current oscillations are observed with an amplitude which depends strongly on the HF content of the electrolyte. Electrochemical, scanning electron microscope and X-ray photoelectron spectroscopy investigations show that the porous layer forms under a competition of formation and oxide dissolution up to a limiting thickness of and that the time scale for complete self-ordering for the investigated systems is in the order of several hours. © 2003 The Electrochemical Society. All rights reserved.
499 citations
TL;DR: In this paper, a Raman microprobe spectroscopic analysis indicated that the structure of the residual carbon present on the surfaces of the powders differs significantly and accounts for the performance variation.
Abstract: The electrochemical performance of LiFePO 4 samples synthesized by sol-gel or solid-state routes varies considerably, although their physical characteristics are similar. Raman microprobe spectroscopic analysis indicated that the structure of the residual carbon present on the surfaces of the powders differs significantly and accounts for the performance variation. Higher utilization is associated with a larger ratio of sp 2 -coordinated carbon, which exhibits better electronic properties than disordered or sp 3 -coordinated carbonaceous materials. Incorporation of naphthalenetetracarboxylic dianhydride during synthesis results in a more graphitic carbon coating and improves utilization of LiFePO 4 in lithium cells, although the total carbon content is not necessarily higher than that of samples prepared without the additive. This result suggests that practical energy density need not be sacrificed for power density, provided that carbon coatings are optimized by carefully choosing additives.
458 citations
TL;DR: The properties of amorphous 250 nm and 1 μm silicon films deposited by radiofrequency (RF) magnetron sputtering on copper foil are investigated using X-ray diffraction, scanning electron microscopy (SEM), and electrochemical methods as mentioned in this paper.
Abstract: The properties of amorphous 250 nm and 1 μm silicon films deposited by radio-frequency (rf) magnetron sputtering on copper foil are investigated using X-ray diffractιon, scanning electron microscopy (SEM), and electrochemical methods. Galvanostatic half-cell electrochemical measurements conducted between 0.02 and 1.2 V using a lithium counter electrode have shown that the 250 nm Si thin films exhibit an excellent reversible specific capacity of nearly 3500 mAh/g when tested for 30 cycles. The high reversible capacity and excellent cyclability of the 250 nm sputtered silicon thin films suggest excellent adhesion between Si and Cu leading to high capacity retention. SEM analysis conducted on the 250 nm Si films after the 30th charge suggests the good adhesion of the ∼2 μm diam "plates" of silicon to the copper substrate.
441 citations
TL;DR: In this paper, a model is advanced in which lithium diffuses through a layer of ZPC to react with Si: growing ZPCs plastically deforms where necessary. And vacancies coalesce to form voids at the ZPC/Si interface, and the voids appear as a fine pattern of cracks, looking like dried mud.
Abstract: Pillar arrays fabricated on silicon substrates have been tested as potential anodes for lithium batteries. Electrodes of array characteristics, diameter 580 ′ 150 nm: fractional surface coverage 0.34: height 810 nm are reported here. Cyclic voltammetry (CV) and cyclic galvanostatic tests of alloying/dealloying of electrochemically produced lithium with silicon were carried out, and results correlated with SEM studies. Aerial current densities in the low and fractional mA cm - 2 , and voltage 25 mV to 2 V (vs. L/Li + ) were used. CV features correspond to various Zintl phase compounds (ZPCs). Structured electrodes of Si pillars maintained their structural integrity throughout cycling; planar Si electrodes showed cracks (2 μm features) after 50 cycles. A model is advanced in which lithium diffuses through a layer of ZPC to react with Si: growing ZPCs plastically deforms where necessary. Upon lithium dealloying vacancies coalesce to form voids at the ZPC/Si interface, Si rejoins the substrate. or precipitates out as a nanocrystalline material, and the voids appear as a fine pattern of cracks, looking like dried mud. The extra surface area that a pillar structure can confer on Si electrodes is essential and makes it practical to consider the possible eventual use of such anodes in integrated battery structure;.
383 citations
TL;DR: In this paper, a novel carbothermal reduction (CTR) method was used to synthesize the electroactive materials LiFePO 4 and LiFe 0. 9 Mg 0. 1 PO 4.
Abstract: The electroactive materials LiFePO 4 and LiFe 0 . 9 Mg 0 . 1 PO 4 have been synthesized by a novel carbothermal reduction (CTR) method. The transition metal reduction and lithium incorporation processes are each facilitatedby the high temperature carbothermal reaction based on the C → CO transition. These CTR conditions favor stabilization of the iron as Fe 2 + as well as offering some control of the product morphology and conductivity. Electrochemical evaluation of the CTR LiFe 0 . 9 Mg 0 . 1 PO 4 reveals a lithium insertion plateau around 3.4 V vs. Li together with a specific capacity of over 150 mAh/g. Differential capacity data confirm the two-phase nature of the insertion reactions as well as the outstanding ionic reversibility. Few technical obstacles have been encountered in scaling the CTR process from a laboratory process to that required for pilot production.
329 citations
TL;DR: In this article, the authors presented preliminary performance data for a novel sodium-ion cell based on a hard chemistry, which was prepared by a simple incorporation reaction involving vanadium(III) phosphate, and NaF.
Abstract: Preliminary performance data is presented for a novel sodium-ion cell based on a hard chemistry. To our knowledge this is the first time that a viable sodium-ion system based on a polyanion cathode material has been demonstrated. The was prepared by a simple incorporation reaction involving vanadium(III) phosphate, and NaF. The hard carbon was from a commercial source. Constant current cycling indicated reversible alkali-ion insertion behavior for the fluorophosphate material, while the generally symmetrical nature of the charge/discharge curves indicated the energetic reversibility of the insertion system. The average discharge voltage for the sodium-ion cells was demonstrated to around 3.7 V, a figure comparable with commercially available lithium-ion cells. The reversible specific capacities for the cathode and anode active materials were determined to be 82 and 202 mAh/g, respectively. Representative test cells cycled more than 30 times before their discharge capacity had declined to less then 50% of the original. The relatively high first cycle charge inefficiency is thought to be due to irreversible passivation reactions occurring at the carbon surface. Significant performance enhancements may be made by optimization of the electrolyte system and improving the active material mass balance. In summary, low overvoltage, good insertion reversibility, and reasonable capacity retention characterize this fluorophosphate-based sodium-ion cell. © 2002 The Electrochemical Society. All rights reserved.
322 citations
TL;DR: In this paper, thermal pyrolysis of polyvinyl chloride with nanosized silicon and fine graphite particles at 900°C produces a novel Si/C composite for lithium storage material.
Abstract: Thermal pyrolysis of polyvinyl chloride dispersed with nanosized silicon and fine graphite particles at 900°C produces a novel Si/C composite for lithium storage material. Incorporated silicon provides major capacity for lithium insertion, while the introduction of graphite component suppresses the initial irreversibility and hysteresis between charge and discharge caused by pyrolyzed carbon. The first cycle efficiency of the composite is about 85%. The large reversible capacity of ca. 700 mAh/g and good cyclability indicates that such Si/C composite may be a useful alternative to conventional graphite-based anode materials for lithium-ion cells.
242 citations
TL;DR: In this paper, the reaction mechanism in atomic layer deposition (ALD) of ruthenium from biscyclopentadienyl ruthensium (RuCp 2 ) and oxygen were studied in situ with a quadruple mass spectrometer (QMS) and a quartz crystal microbalance (QCM).
Abstract: Reaction mechanisms in atomic layer deposition (ALD) of ruthenium from bis(cyclopentadienyl)ruthenium (RuCp 2 ) and oxygen were studied in situ with a quadruple mass spectrometer (QMS) and a quartz crystal microbalance (QCM). In addition, QMS was used to study ALD of platinum from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe 3 ) and oxygen. The QMS studies showed that the reaction by-products H 2 O and CO 2 were released during both the oxygen and the metal precursor pulses. Adsorbed oxygen layer on the metal surface thus oxidizes part of the ligands during the metal precursor pulse. The remaining ligand species become oxidized and a new layer of adsorbed oxygen forms on the surface during the following oxygen pulse. The QCM analysis of the ruthenium process showed a mass decrease during the RuCp 2 pulse and a mass increase during the oxygen pulse, which further supports the proposed mechanism.
226 citations
TL;DR: In this article, electrical conductivity at the microscopic grain level has been measured in densely sintered polycrystalline samples of LiFePO 4 and Li 0. 9 9 Nb 0. 0 1 FePO 4, using a four-point microcontact technique.
Abstract: Electrical conductivity at the microscopic grain level has been measured in densely sintered polycrystalline samples of LiFePO 4 and Li 0 . 9 9 Nb 0 . 0 1 FePO 4 , using a four-point microcontact technique. The absolute value of conductivity as well as its spatial variability have been measured, and are consistent with previously reported bulk measurements. The results support the interpretation of the conductivity increase upon doping of LiFePO 4 as a lattice effect.
199 citations
TL;DR: In this paper, a hybrid electrochemical capacitor using MnO 2 and Fe 3 O 4 as active material for the positive and the negative electrode, respectively, has been designed, and the electrodes have been individually tested in a mild aqueous electrolyte (0.1 M K 2 SO 4 ) to define the adequate balance of active material in the capacitor as well as the working voltage of a capacitor based on these two electrodes.
Abstract: A hybrid electrochemical capacitor using MnO 2 and Fe 3 O 4 as active material for the positive and the negative electrode, respectively, has been designed. The electrodes have been individually tested in a mild aqueous electrolyte (0.1 M K 2 SO 4 ) to define the adequate balance of active material in the capacitor as well as the working voltage of a capacitor based on these two electrodes. The specific capacitances of MnO 2 and Fe 3 O 4 were 150 ′ 10 and 75 ′ 8 F/g, respectively whereas the specific capacitance of the Fe 3 O 4 /MnO 2 capacitor was equal to about 20 F/g of active material. The hybrid electrochemical capacitor has been cycled between 0 and 1.8 V for over 5000 constant current charge/discharge cycles. A real energy density of 7 Wh/kg was reproducibly measured with a real power density up to 820 W/kg.
TL;DR: In this paper, thin Sn-Ni alloy films containing various Sn/Ni ratios were prepared by electrodeposition and characterized as lithium-ion secondary battery anodes, and the initial drop in discharge capacity varied with the Sn content of the sample.
Abstract: Thin Sn-Ni alloy films containing various Sn/Ni ratios were prepared by electrodeposition and characterized as lithium-ion secondary battery anodes. The initial drop in discharge capacity varied with the Sn content of thesample; i.e., for samples with 54 atom % Sn and 62 atom % Sn, the drop was less than 100 mAh/g, whereas for those with 84 atom % Sn and 92 atom % Sn, the drop exceeded 500 mAh/g. Among these thin films, the 62 atom % Sn film showed the highest reversible capacity of ca. 650 mAh/g at about the 70th cycle, whereas the other samples (54 atom % Sn, 84 atom % Sn. 92 atom %. Sn) showed a capacity of 300 mAh/g.
TL;DR: The surface of LiCoO 2 cathodes was modified with Al 2 O 3, TiO 2, and ZrO 2 by a chemical processing procedure followed by heat treatment at 300°C in air for 4 h as mentioned in this paper.
Abstract: The surface of LiCoO 2 cathodes was modified with Al 2 O 3 , TiO 2 , and ZrO 2 by a chemical processing procedure followed by heat treatment at 300°C in air for 4 h. The surface-modified LiCoO 2 samples show much better capacity retention at both 25 and 60°C than the unmodified LiCoO 2 cathode to higher cutoff charge voltages of as high as 4.7 V vs. lithium. For example, Al 2 O 3 -modified LiCoO 2 shows approximately 180 mAh/g at 4.5 to 3.2 V with a capacity fade of only 8% in 100 cycles, compared to 32% for the unmodified LiCoO 2 . Transmission electron microscopic studies reveal that the guest materials are present as loose oxides (Al 2 O 3 and ZrO 2 ) or as monolayers (TiO 2 ) on the surface of LiCoO 2 particles. The improved capacity retention and the higher reversible capacity (180 mAh/g) of the surface-modified LiCoO 2 compared to the unmodified LiCoO 2 (140 mAh/g) could be due to a suppression of the chemical and structural instabilities of the charged Li 1 - x CoO 2 cathodes and/or reduction of interparticle stresses and strains.
TL;DR: In this article, the solid electrolyte interface on graphite formed by LiBOB-based electrolyte was investigated by X-ray photoelectron spectroscopy, and it was shown that due to the BOB anion presence, the content of semicarbonate-like components in the graphite/electrolyte interface increases significantly, as indicated by the conspicuous peak located at 289 eV.
Abstract: To understand the source of thermal stability of LiBOB-based electrolyte in lithium-ion cells as well as its unique ability to stabilize graphitic anodes even in the strongly exfoliating solvent propylene carbonate (PC), the solid electrolyte interface on graphite formed by LiBOB-based electrolyte was investigated by X-ray photoelectron spectroscopy. Preliminary results show that, due to the BOB anion presence, the content of semicarbonate-like components in the graphite/electrolyte interface increases significantly, as indicated by the conspicuous peak located at 289 eV. These components, believed to originate from the oxalato moiety of the anion, are mainly responsible for the protection of graphitic anodes, either at elevated temperatures or in the presence of PC. © 2003 The Electrochemical Society. All rights reserved.
TL;DR: In this paper, a commercial sample of LiCoO 2 was coated with ZrO 2, SiO 2, and Al 2 O 3 for comparative studies, and a heat-treated control sample was charged and discharged between 3.6 and 4.5 V at a C/3 rate.
Abstract: It has been reported that LiCoO 2 coated with a metal oxide layer can deliver a capacity in excess of 140 mAh/g with improved capacity retention. Here, a commercial sample of LiCoO 2 was coated with ZrO 2 , SiO 2 , and Al 2 O 3 for comparative studies. Li/LiCoO 2 cells using the coated LiCoO 2 samples and a heat-treated control sample were charged and discharged between 3.6 and 4.5 V at a C/3 rate. All samples showed excellent capacity retention compared to the as-received commercial sample. Unlike literature reports, we find the capacity retention of coated LiCoO 2 is independent of the specific oxide used for the coating.
TL;DR: In this paper, the results of Raman analysis indicated that no free PC molecules are present in the concentrated solution, which suggested that the ion/solvent interactions would be an important factor that determines the ability of stable surface film formation in PC-based solutions.
Abstract: Electrochemical lithium intercalation within graphite was investigated in propylene carbonate (PC) containing different concentrations, 0.82 and 2.72 mol dm - 3 , of bis(perfluoroethylsulfonyl)imide, LiN(SO 2 C 2 F 5 ) 2 . Lithium ion was reversibly intercalated into and deintercalated from graphite in the latter concentrated solution in spite of the use of pure PC as a solvent, whereas ceaseless solvent decomposition and intensive exfoliation of graphene layers occurred in the former solution. X-ray diffraction analysis revealed that a stage I graphite intercalation compound was formed alter being fully charged in the 2.72 mol dm - 3 solution. The results of Raman analysis indicated that no free PC molecules are present in the concentrated solution, which suggested that the ion/solvent interactions would be an important factor that determines the ability of stable surface film formation in PC-based solutions.
TL;DR: Sulfonated poly(ether ether ketone) (SPEEK) with different degrees of sulfonation has been prepared and evaluated as proton exchange membrane electrolytes in direct methanol fuel cells (DMFCs).
Abstract: Sulfonated poly(ether ether ketone) (SPEEK) with different degrees of sulfonation has been prepared and evaluated as proton exchange membrane electrolytes in direct methanol fuel cells (DMFCs). The membranes have been characterized by ion-exchange capacity, proton conductivity, and liquid uptake measurements. The proton conductivity of the SPEEK membranes increases with increasing sulfonation level, and are lower than that of Nafion. The percent liquid uptake increases with increasing temperature, methanol concentration, and degree of sulfonation. Within a narrow range of sulfonation of ∼50%, the SPEEK membranes exhibit electrochemical performances comparable to or exceeding that of Nafion at 65°C, making it an attractive low-cost alternative to Nafion. The better performance of the SPEEK membranes is due to the suppression of methanol permeability as indicated by a lower methanol crossover current density at the cathode.
TL;DR: In this paper, high energy mechanical milling was used to synthesize amorphous silicon and nanocrystalline titanium boride nanocomposites with a stable capacity of ∼400 mAh/g.
Abstract: Silicon and titanium boride nanocomposites were synthesized using high-energy mechanical milling. The nanocomposites obtained after mechanical milling consist of amorphous silicon and nanocrystalline titanium boride. The nanocomposite containing 40 mol % silicon obtained after milling for 20 h exhibits a stable capacity of ∼400 mAh/g. X-ray diffraction and scanning electron microscopy analyses indicated that the nanocomposite retains its initial phase and microstructure during electrochemical cycling. Premilling of the inactive TiB 2 component appears to increase the stability of the capacity of the nanocomposite electrodes due to a probable homogeneous distribution of the induced stress during cycling.
TL;DR: In this article, a single-step deposition of fine trenches by direct copper electrodeposition onto a ruthenium banier was demonstrated, where the ruthensium layer, as well as an adhesion promoting titanium or tantalum layer, was deposited by physical vapor deposition onto patterned silicon dioxide.
Abstract: Superfilling of fine trenches by direct copper electrodeposition onto a ruthenium ban ier is demonstrated. The ruthenium layer, as well as an adhesion promoting titanium or tantalum layer, was deposited by physical vapor deposition onto patterned silicon dioxide. Copper was deposited from an electrolyte previously shown to yield superconformal feature filling on copper seeded features. The single-step deposition process offers significant processing advantages over conventional damascene processing.
TL;DR: In this article, the surfaces of graphite anodes extracted from Li-ion cells with Fourier transform infrared spectroscopy using attenuated total reflection geometry were examined, and they were subjected to calender aging (60% state of charge) at 55°C.
Abstract: We examined the surfaces of graphite anodes extracted from Li-ion cells with Fourier transform infrared spectroscopy using attenuated total reflection geometry. The cells were of the 18650-type and subjected to calender aging (60% state of charge) at 55°C. The composition of the film on an anode from a control cell (not aged) is composed of lithium oxalate (Li 2 C 2 O 4 ), lithium carboxylate (RCOOLi), and lithium methoxide (LiOCH 3 ). After aging, there is also lithium hydroxide (LiOH) and methanol (CH 3 OH), and in some cases lithium hydrogen carbonate (LiHCO 3 ), probably due to the reaction of water with the methoxide and oxalate. There is substantial variation in the relative amounts of the five compounds over the surfaces of the electrodes. Alkyl carbonates may form early on, but decompose to more "inorganic" compounds with aging. The multicomponent composition reflects the complex chemistry of passive film formation in real Li-ion cells.
TL;DR: In this paper, an exploratory study of H 2 S poisoning of membrane electrode assemblies (MEAs) in proton exchange membrane fuel cells (PEMFCs) consisting of Pt and Pt-Ru alloy electrodes is presented.
Abstract: An exploratory study of H 2 S poisoning of membrane electrode assemblies (MEAs) in proton exchange membrane fuel cells (PEMFCs) consisting of Pt and Pt-Ru alloy electrodes is presented. Steady-state polarization curves arereported for each electrode after exposure to 50 ppm H 2 S at 70°C. Significant findings include (i) partial recovery of the MEA after 3.8 h of exposure to H 2 S: (ii) the degree of the recovery is influenced by the electrochemical oxidation of two surface species observed during cyclic voltammetry experiments; (iii) in contrast to CO poisoning, Ru has no effect on increasing MEA tolerance toward H 2 S poisoning; and (iv) increasing the Pt loading by 60% appears to quadruple the partially recovered current density at 0.6 V (i.e., 0.125 A/cm 2 for Pt-Ru alloy and 0.575 A/cm 2 for Pt electrodes) after exposure to neat H 2 for 24 h.
TL;DR: The structural and chemical stabilities of Li 1 - x CoO 2 - Φ and Li 1- x Ni 0. 8 5 Co 0. 1 5 O 2 − Φ [0 ≤ (1 - x) ≤ 1] cathodes have been investigated by chemically extracting lithium with an acetonitrile solution of NO 2 BF 4 as discussed by the authors.
Abstract: The structural and chemical stabilities of Li 1 - x CoO 2 - Φ and Li 1 - x Ni 0 . 8 5 Co 0 . 1 5 O 2 - Φ [0 ≤ (1 - x) ≤ 1] cathodes have been investigated by chemically extracting lithium with an acetonitrile solution of NO 2 BF 4 . The Li 1 - x CoO 2 - Φ and Li 1 - x Ni 0 . 8 5 Co 0 . 1 5 O 2 - Φ systems maintain the initial 03-type structure, respectively, for 0.5 ≤ (1 - x) ≤ 1 and 0.3 ≤ (1 - x) « 1. While Li 1 - x CoO 2 - Φ begins to form a P3-type phase for (1 - x) < 0.5, Li 1 - x Ni 0 . 8 5 Co 0 . 1 5 O 2 - Φ begins to form a new 03-type phase, designated as 03' phase, for (1 - x) < 0.3. The P3-type and the 03' phases have smaller c parameters than do the 03-type phase and oxygen contents of <2, resulting in a loss of oxygen from the lattice for (1 - x) < 0.5 and (1 - x) < 0.3, respectively, for Li 1 - x CoO 2 - Φ and Li 1 - x Ni 0 . 8 5 Co 0 . 1 5 O 2 - Φ . The loss of oxygen is also confirmed for electrochemically charged samples. The formation of new phases with lower oxygen contents at different levels of charge, (1 - x) < 0.5 vs. ( 1 - x) < 0.3, for the two systems may play a role in limiting the practical capacities of the two systems (140 vs. 180 mAh/g).
TL;DR: In this article, the electrochemical reaction of lithium with the metal phosphide FeP 2 was investigated using electrochemical studies combined with X-ray diffraction, Xray absorption spectroscopy, and magnetic measurements.
Abstract: The electrochemical reaction of lithium with the metal phosphide FeP 2 is reported. Li uptake in this material was investigated using electrochemical studies combined with X-ray diffraction, X-ray absorption spectroscopy,and magnetic measurements. The uptake of six Li during the first discharge leads to a specific capacity of 1365 mAh/g, and an amorphous phase retaining substantial Fe-P bonding that displays superparamagnetic behavior and an extremely low transition temperature. Upon charge, 5.5 lithium can be extracted from this metastable ternary "Li-Fe-P" phase, leading to a reversible capacity of 1250 mAh/g. The low (ca. 10-15%) irreversibility exhibited by FeP 2 makes it an interesting candidate in the search for new negative electrode materials.
TL;DR: In this article, solid electrolyte interface (SEI) formed on graphitic anode in electrolyte containing a salt, lithium bis(oxalato)borate (LiBOB), was investigated using electrochemical means, and an irreversible reduction process was found for LiBOB on graphite anode at ca. 1.6 V vs. Li.
Abstract: Solid electrolyte interface (SEI) formed on graphitic anode in electrolyte containing a salt, lithium bis(oxalato)borate (LiBOB), was investigated using electrochemical means, and an irreversible reduction process was found for LiBOB on graphitic anode at ca. 1.6 V vs. Li. To ascertain whether this process is responsible for the unique LiBOB property in stabilizing graphene structure against propylene carbonate (PC), we systematically interrupted the lithiation of graphitic anodes in LiBOB-electrolytes at a series of potentials and then tested the survivability of these preformed anodes in PC solution of LiPF 6 , an electrolyte composition known to exfoliate graphite materials readily. The results demonstrate that the formation of a functioning SEI is completed at potentials around 0.50 V vs. Li, and confirmed that BOB-anion plays a critical role in the effectiveness of the formed SEI to protect the graphene structure from exfoliation even in PC.
TL;DR: The surface chemistry of Carbon-Treated LiFePO4 Particles for Li-Ion Battery Cathodes Studied by PES is described in this article, where the authors show that
Abstract: Surface Chemistry of Carbon-Treated LiFePO4 Particles for Li-Ion Battery Cathodes Studied by PES
TL;DR: In this paper, the effect of adding dopant levels of precious metals (PM: Pt, Rh, or Pd) into solid oxide fuel cell (SOFC) anodes based on carbon, ceria, and yttria-stabilized zirconia (YSZ) was examined.
Abstract: The effect on cell performance of adding dopant levels of precious metals (PM: Pt, Rh, or Pd) into solid oxide fuel cell (SOFC) anodes based on carbon, ceria, and yttria-stabilized zirconia (YSZ) was examined. The PM-doped anodes remained stable in dry CH 4 and n-butane over a period of at least 24 h. While maximum power densities for H 2 and n-butane increased by almost a factor of two upon addition of PM, the maximum power density for CH 4 increased by a factor of almost 10 over that measured on a Cu-ceria-YSZ anode, to 280 mW/cm 2 at 973 K. The open-circuit voltages (OCVs) were also measured for CH 4 and n-hutane as a function of H 2 O and CO 2 concentrations. The addition of PM dopants led to a significant increase in the OCV for CH 4 and n-butane, although the OCV remained lower than the theoretical Nernst potentials. The differences between the theoretical and measured OCV are attributed to barriers to surface reaction, which in turn can be decreased through improved catalytic properties.
TL;DR: In this paper, anion-exchange anticorrosion pigments consisting of nitrate, carbonate, and chromate exchanged hydrotalcite (HT) are shown to effectively inhibit the propagation of filiform corrosion (FFC) on organic coated AA2024-T3 aluminum alloy.
Abstract: Novel anion-exchange anticorrosion pigments consisting of nitrate, carbonate, and chromate exchanged hydrotalcite (HT) are shown to effectively inhibit the propagation of filiform corrosion (FFC) on organic coated AA2024-T3 aluminum alloy. The HT-pigments are dispersed in polyvinyl butyral (PVB) coatings applied to the AA2024-T3 surface. Following FFC initiation by application of aqueous HCl to a penetrative coating defect, the time-dependent extent of coating delamination is determined both optically and by means of repeated in situ scanning using a scanning Kelvin probe apparatus. All HT-pigments are shown to profoundly reduce rates of coating delamination by comparison to unpigmented samples. However, inhibitor efficiency is dependent upon the exchangeable anion and increases in the order © 2003 The Electrochemical Society. . All rights reserved.
TL;DR: In this paper, the electrolyte properties of Li(Li{sub 0.2}Ni{sub 1.6}O{sub 2} cells were studied by galvanostatic cycling and showed that Li ions in the transition metal layer were irreversibly extracted during charging at a voltage higher than 4.5 V.
Abstract: Electrochemical properties of Li(Li{sub 0.2}Ni{sub 0.2}Mn{sub 0.6})O{sub 2}, synthesized by a sol-gel method, were studied by galvanostatic cycling. When the Li/Li(Li{sub 0.2}Ni{sub 0.2}Mn{sub 0.6})O{sub 2} cell was cycled at 2.0--4.6 V, the material showed a long, irreversible plateau at 4.5--4.6 V and exhibited very high initial charge capacity of 240 mAh/g, which is much larger than a theoretical value for the reaction of Li(Li{sup +}{sub 0.2}Ni{sup 2+}{sub 0.2}Mn{sup 4+}{sub 0.6})O{sub 2} {yields} Li{sub 0.6}(Li{sup +}{sub 0.2}Ni{sup 4+}{sub 0.2}Mn{sup 4+}{sub 0.6})O{sub 2} + 0.4Li (126 mAh/g). Discharge capacity of the material gradually increased from 155 at the first cycle to 205 mAh/g at the tenth cycle and was stabilized afterward. From the ex situ X-ray study, we found that Li ions in the transition metal layer were irreversibly extracted during charging at a voltage higher than 4.5 V; the diffraction peaks corresponding to Li in the transition metal layer were hardly observed in the cathode material after extended cycling. The Li/Li(Li{sub 0.2}Ni{sub 0.2}Mn{sub 0.6})O{sub 2} cell that was cycled at 2.0--4.3 V showed stable but very small capacity (69 mAh/g) and Li in the transition metal layer remained almost intact. When the cell was initially charged to 4.6 V and thenmore » cycled at 2.0--4.3 V, the cathode material showed higher capacity (114 mAh/g) than the one cycled at 2.0--4.3 V.« less
TL;DR: In this paper, an ionic conducting-type Gd 0. 2 Ce 0. 8 (NO 3 ) x nitrite salt solution was impregnated into the LSM structure, and the electrochemical activity of LSM electrodes for the O 2 reduction reaction was substantially enhanced.
Abstract: Conventional (La, Sr)MnO 3 (LSM) electrodes modified by ion impregnation methods showed promising potential as cathodes for intermediate temperature solid oxide fuel cells. After impregnation of ionic conducting-type Gd 0 . 2 Ce 0 . 8 (NO 3 ) x nitrite salt solution into the LSM structure, electrochemical activity of LSM electrodes for the O 2 reduction reaction was substantially enhanced. At 700°C, the electrode polarization resistance of impregnated LSM electrodes decreased to 0.72 Ω cm 2 as compared to 26.4 Ω cm 2 for pure LSM electrodes, a reduction in electrode polarization resistance by 36 times. The polarization losses were also reduced substantially. At 300 mA cm - 2 and 700°C, overpotential for the O 2 reduction was reduced from 0.79 V on pure LSM to 0.19 V on impregnated LSM electrodes, a reduction in overpotential by four times. Ion-impregnated LSM electrodes showed better performance than those of LSM/Y 2 O 3 -ZrO 2 and LSM/(Gd,Ce)O 2 composite electrodes as reported in the literature.
TL;DR: In this paper, the bottom-up filling behavior is due to CuCl crystals formed by a synergistic effect between NIPS and chloride ions, which results in acceleration of copper growth in via holes.
Abstract: Blind vias with hole sizes of 85 and 110 μm formed by laser ablation on printed circuit boards were employed for investigation of filling by copper electroplating. The plating solution formulated was composed of acid copper sulfate, polyethylene glycol, 3-mercapto-1-propanesulfonate (MPS). and chloride ions. A "bottom-up" filling behavior had been observed with an appropriate MPS concentration. When MPS concentration was higher than 5.6 X 10 - 6 mol/L, conformal deposition occurred. However, this situation could be altered by adding more chloride ions into the plating solution to recover the behavior of bottom-up filling. Scanning electron microscopy showed that the recovely of bottom-up filling behavior is due to CuCl crystals formed by a synergistic effect between NIPS and chloride ions. The synergistic effect results in acceleration of copper growth in via holes. These experimental results agree with the curvature-enhanced accelerator coverage mechanism.