Electrochemical Insertion Of Lithium Ions Research Articles

Study of a Rechargeable Lithium-Ion Battery Based on a Copper Hexacyanoferrate Cathode

Rechargeable lithium-ion batteries are among the most promising battery technologies to meet energy conversion and storage requirements. However, this technology is still limited due to its high cost, which prevents its use on a large scale. Therefore, cheaper energy storage systems with long cycle life, high power/efficiency, and safety are in great demand and interest. Prussian blue analogs are promising candidates for use in large-scale energy storage applications due to their long-life cycles, high power density, and high energy efficiency [1]. Along with the change of the transition metal, some structural parameters and some fundamental properties of these compounds can be changed, affecting some parameters such as the battery's storage capacity.This work studied the electrochemical insertion of lithium ions into Copper Hexacyanoferrate (CuHCF). This compound was synthesized by a hydrothermal process using a factorial design for determining the significance variables, i. e., precursor concentrations, temperature, and reaction time, on the electrochemical performance of the battery. The samples obtained were characterized by FESEM, TEM, XRD, and TGA. The results show cubic structures with a high degree of crystallinity and an evident dependence of the crystallite size (50 - 140 nm) with the variation of the synthesis conditions. Finally, lithium-ion batteries were measured using a CuHCF cathode (theoretical charge 85.1 mAhg-1). The capacity values depended on the crystallite size, obtaining the best results in the synthesis under lower concentrations, reaction time, and temperature. This sample was submitted to deep charge/discharge cycles at a rate of C/20, where the capacity value was close to 60 mAhg-1 (right image). This demonstrates the influence of the crystallite size on the material's performance, managing to find the optimal synthesis conditions to maximize the battery capacity. References. [1] 1. Marzhana Omarova, Aibolat Koishybay, Nulati Yesibolati, Almagul Mentbayeva, Nurzhan Umirov, Kairat Ismailov, Desmond Adair, Moulay-Rachid Babaa, Indira Kurmanbayeva, Zhumabay Bakenov, Electrochim. Acta, 184 (2015) 58-63. Figure 1

Low-Voltage, CMOS-Free Synaptic Memory Based on LiXTiO2 Redox Transistors.

Neuromorphic computers based on analogue neural networks aim to substantially lower computing power by reducing the need to shuttle data between memory and logic units. Artificial synapses containing nonvolatile analogue conductance states enable direct computation using memory elements; however, most nonvolatile analogue memories require high write voltages and large current densities and are accompanied by nonlinear and unpredictable weight updates. Here, we develop an inorganic redox transistor based on electrochemical lithium-ion insertion into LiXTiO2 that displays linear weight updates at both low current densities and low write voltages. The write voltage, as low as 200 mV at room temperature, is achieved by minimizing the open-circuit voltage and using a low-voltage diffusive memristor selector. We further show that the LiXTiO2 redox transistor can achieve an extremely sharp transistor subthreshold slope of just 40 mV/decade when operating in an electrochemically driven phase transformation regime.

Electrochemical lithium intercalation chemistry of condensed molybdenum metal cluster oxide: LiMo4O6

The electrochemical lithium-ion intercalation properties of molybdenum metal-cluster oxide LixMo4O6 (0.33 ≤ x ≤ 1.0) in an organic electrolyte of 1.0M LiPF6 in ethylene carbonate/dimethyl carbonate (1:2v/v) were characterized for the first time. Li0.66Mo4O6 (tetragonal, P4/mbm, a = 9.5914(3) Å, c = 2.8798(1) Å, V = 264.927(15) Å3, Z = 2) was prepared via ion-exchange of indium and lithium ions from InMo4O6 (tetragonal, P4/mbm, a = 9.66610(4) Å, c = 2.86507(2) Å, V = 267.694(2) Å3, Z = 2), which was first synthesized from a stoichiometric mixture of In, Mo, and MoO3 via a solid-state reaction for 11h at 1100°C. Then, Li0.33Mo4O6 was obtained via electrochemical charge of the electrode at 3.4V vs. Li. The electrochemical lithium-ion insertion into Li0.33Mo4O6 occurs stepwise: three separate peaks were observed in the cyclic voltammogram and three quasi-plateaus in the galvanostatic profile, indicating a complicated intercalation mechanism. However, examination of the structural evolution of LixMo4O6 during the electrochemical cycle indicated a reversible reaction over the measured voltage range (2.0–3.2V) and x range (0.33 ≤ x ≤ 1.00). Despite the excellent electrochemical reversibility, LixMo4O6 showed poor rate performance with a low capacity of 36.3mAhg−1 at a rate of 0.05C. Nonetheless, this work demonstrates a new structural class of lithium cathode materials with condensed metal clusters and 1D tunnels, and provides a host material candidate for multivalent-ion batteries.

Scanning Electrochemical Microscopy Applied to the Investigation of Lithium (De‐)Insertion in TiO2

AbstractThe electrochemical insertion of lithium ions in anatase TiO2 nanoparticles was investigated by scanning electrochemical microscopy in the feedback mode of operation using ferrocene as reporting redox couple at different potentials in presence and absence of lithium ions. By fixing the position of the tip while performing cyclic voltammetry at the TiO2 paste electrode, the formation of the solid electrolyte interphase (SEI) on the surface of titania was followed in situ. Different scan rates have been used to study the kinetics of SEI formation.

Nickel/carbon core/shell nanotubes: Lanthanum nickel alloy catalyzed synthesis, characterization and studies on their ferromagnetic and lithium-ion storage properties

A method was developed to synthesize ferromagnetic nickel core/carbon shell nanotubes (Ni/CNTs) by chemical vapor deposition using Pauli paramagnetic lanthanum nickel (LaNi5) alloy both as a catalyst and as a source for the Ni-core. The Ni-core was obtained through oxidative dissociation followed by hydrogen reduction during the catalytic growth of the CNTs. Transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) analyses reveal that the Ni-core exists as a face centered cubic single crystal. The magnetic hysteresis loop of Ni/CNTs particle shows increased coercivity (446.42Oe) than bulk Ni at room temperature. Furthermore, the Ni/CNTs core/shell particles were investigated as anode materials in lithium-ion batteries. The Ni/CNTs electrode delivered a high discharge capacity of 309mAhg−1 at 0.2C, and a stable cycle-life, which is attributed to high structural stability of Ni/CNTs electrode during electrochemical lithium-ion insertion and de-insertion redox reactions.

Kinetics of electrochemical insertion of lithium ion into LiFePO 4 from aqueous 2 M Li 2SO 4 solution studied by potentiostatic intermittent titration technique

Potentiostatic intermittent titration technique (PITT) has been used to study the lithium ion insertion into LiFePO 4 from aqueous 2 M Li 2SO 4 electrolyte along with cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques. The current–time response to an applied potential step has been discussed for lithium insertion into LiFePO 4 from aqueous electrolyte and it is compared with that obtained with an organic electrolyte. The PITT technique is very useful in describing the whole intercalation mechanism. The effects of ohmic potential drops and charge-transfer resistances have been taken into account while predicting the current transients obtained with aqueous electrolyte and non-aqueous electrolyte. The deviation of current transients from ideal Cottrell behavior has been discussed in aqueous electrolyte and it is compared with that in presence of non-aqueous electrolyte. The characteristic diffusion time constant ( t o) in 2 M Li 2SO 4 is found to be 4.71 s and that in non-aqueous LiAsF 6/EC–DMC electrolyte is 248 s. The chemical diffusion coefficient ( D), an important kinetic parameter, calculated from PITT during intercalation process is found to be varying between 10 −12 and 10 −14 cm 2 s −1 in aqueous electrolyte and between 10 −13 and 10 −15 cm 2 s −1 in non-aqueous electrolyte.

Influence of graphite surface properties on the first electrochemical lithium intercalation

The electrochemical insertion of lithium ions into graphite materials having different surface chemistry and defect concentration was studied during the first cycle in half-cell containing 1 M LiPF 6 in an electrolytic solvent mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The graphite surface properties were varied by thermal treatments in either hydrogen, oxygen, or nitrogen oxide or chemical treatment in boiling nitric acid. The influence of the surface modifications on the course of the first electrolyte reduction was investigated. The surface group chemistry was analyzed by temperature-programmed desorption coupled with mass spectrometry. The surface defect concentration was determined in terms of the active surface area (ASA) measured by oxygen chemisorption and a subsequent temperature-programmed desorption. The experimental results showed that the ASA parameter governs the exfoliation tendency of the graphite negative electrode material with the existence of a critical value below which the graphite systematically exfoliates. The specific charge loss during the first electrochemical insertion of lithium and the exfoliation behavior of the graphite negative electrode material are not influenced by the type and amount of oxygen surface groups. But hydrogen present on the graphite surface increased the graphite exfoliation tendency even for graphite materials with an ASA above the critical value.

Structure change analysis in γ-Fe 2O 3/carbon composite in the process of electrochemical lithium insertion

It was previously shown that γ-Fe 2O 3/carbon composite synthesized by the aqueous solution method exhibit good high-speed charge/discharge and cycle characteristics as the cathode material in lithium-ion rechargeable batteries. We examined the crystal structure of γ-Fe 2O 3 in γ-Fe 2O 3/carbon composite by X-ray diffraction and the Rietveld analysis before and during electrochemical insertion of lithium ions. Before insertion, the sample has a spinel structure belonging to the Fd3¯ m space group with the following iron occupancies: 8a site, 0.92, 16c site, 0 and 16d site, 0.87. During insertion, iron occupancy at 16d site remains virtually constant, at 8a site decreases from 0.92 to 0, and at 16c site increases from 0 to 0.53. These results suggest that, during insertion, iron migrates from 8a to 16c site. In the most highly lithiated sample, iron occupancy at 8a site decreases to 0 and occupancies at 16c and 16d sites were not equalized. Thus, the crystal structure for this sample belongs not to the Fm3¯ m space group that represents the rock salt structure, but rather to the Fd3¯ m space group.

Colorimetric Determination of Lithium Content in Electrodes of Lithium-Ion Batteries

Graphites, as well as other intercalation materials used in lithium-ion batteries, change their color upon electrochemical insertion of lithium ions. In this study, in situ colorimetry was developed as a straightforward technical method to measure the local state of charge of lithium-ion battery electrodes. A laboratory cell with a glass window was built for in situ characterization of intercalation materials. Calibration curves of red, green, and blue color values vs state of charge were acquired and used for mapping of lithium distribution in battery electrodes. The lithium distribution in anodes of aged lithium-ion batteries was found to be highly heterogeneous.

Structure Change Analysis in γ-Fe2O3 / Carbon Composite in the Process of Electrochemical Lithium Insertion

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Raman study on electrochemical lithium insertion into multiwalled carbon nanotubes

AbstractWe have carried out in situ Raman studies during the electrochemical insertion of lithium ions (Li+) into pristine and thermally treated multiwalled carbon nanotubes (MWNTs). We found an improved structural integrity as well as the removal of defects in the thermally treated tubes. The different Li+ insertion behaviors above 0.5 V in as‐grown and thermally treated tubes could be explained by the presence of defects on the outer surface of the tubes. No change of Raman spectra from 2.8 to 0.8 V is characterized by the coverage of Li+ on the outer surface of tubes, whereas the upshift of G band and the absence of a separated G band below 0.75 V indicate the formation of diluted graphite intercalation below the stage‐2 phase (LiC12). Copyright © 2008 John Wiley & Sons, Ltd.

Submicro- and nanostructural effects on electrical properties of Li0.2V2O5 thin films obtained by atomic layer deposition (ALD)

Dielectric and conductivity spectra of a Li0.2V2O5 thin film were recorded in a broad frequency range 40–1.1×108 Hz at temperature varying between 210 and 300 K. The V2O5 thin film (thickness 260 nm) was deposited on titanium substrate by atomic layer deposition (ALD). An annealing process at 500 °C in air was required to obtain crystallized V2O5. Li0.2V2O5 were obtained by electrochemical insertion of lithium ions within V2O5 thin film. All the data are presented in the form of complex resistivity and permittivity diagrams which have been analyzed in relation to characterizations with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Dc-conductivity σDc of Li0.2V2O5 film is induced by a surface diffusion of small-polarons on particles (submicrostructure) and crystallites (nanostructure), which constitute the film texture.

Electrochemical insertion of lithium ions into disordered carbons derived from reduced graphite fluoride

Both covalent (obtained by direct fluorination at high temperature) and semi-ionic carbon fluorides (synthesized at room temperature) were reduced in order to obtain disordered carbons containing very small content of fluorine and different physical properties according to the reduction treatment (chemical, thermal or electrochemical). After a physical characterization (X-ray diffraction, electron spin resonance and FT-IR spectroscopies), the electrochemical behaviours of the pristine carbon fluorides and of the treated samples were investigated during the insertion of lithium using liquid carbonate-based electrolytes (LiClO 4–EC/PC, 50:50%, v/v). Both galvanostatic and voltammetric modes were performed and revealed that the voltage profiles and the capacities differed according to the starting material and the reduction treatment. Semi-ionic carbon fluoride treated in F 2 atmosphere for 2 h at 150 °C and then chemically reduced in KOH exhibits high reversible capacities (the reversible capacity is 530 mAh g −1 in the second cycle); in this case, the voltage profiles show a large flat portion at potentials lower than 0.3 V which is attributed to the insertion/deinsertion of lithium ions between the small graphene sheets and/or the absorption of pseudo metallic lithium into the microporosity of the sample. Nevertheless, a part of the lithium ions are removed at potentials higher than 0.5 V versus Li +/Li limiting the useful capacity.

Local Structural Characterization for Electrochemical Insertion−Extraction of Lithium into CoO with X-ray Absorption Spectroscopy

Cobalt oxide is known to exhibit a large capacity as a negative electrode in lithium-ion batteries. Here, Co K-edge X-ray absorption spectroscopy (XAS) was used to investigate variations in the local structure during the first electrochemical cycle of the insertion−extraction of lithium into CoO. The XANES and EXAFS spectra in LiyCoO (y: lithium content) varied markedly with the lithium content. The initial insertion of lithium leads to the reduction of Co2+ in the pristine CoO to the reduced metallic Co0 state. The systematic variations observed in intensities of the peaks corresponding to the 1s → 3d and 1s → 4p transitions indicate that the mole ratio of Co to CoO increases gradually with the electrochemical insertion of lithium ions. Insertion of lithium causes the local structure around the Co atoms to become asymmetric. The systematic decrease in the magnitude of the Fourier transform (FT) with increasing amount of inserted lithium is closely related to an increase in static disorder due to the pre...

Electrical and electrochemical characterization of petrol cokes for lithium‐ion cells

Several cokes and graphites have been electrically and electrochemically characterized. The process of electrochemical lithium ion insertion into these materials has been analyzed for the purpose of assessing their performance as electrodes in advanced batteries and as potential candidates to substitute for lithium metal. The results obtained prove the process of electrochemical lithium ion insertion into cokes and graphites to be strongly influenced both by the ordered structure of the starting material and by the nature of the anion of the lithium salt, which is used as electrolyte. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1003–1008, 1999

Electrical and electrochemical characterization of petrol cokes for lithium-ion cells

Several cokes and graphites have been electrically and electrochemically characterized. The process of electrochemical lithium ion insertion into these materials has been analyzed for the purpose of assessing their performance as electrodes in advanced batteries and as potential candidates to substitute for lithium metal. The results obtained prove the process of electrochemical lithium ion insertion into cokes and graphites to be strongly influenced both by the ordered structure of the starting material and by the nature of the anion of the lithium salt, which is used as electrolyte.

A New and Simple Method for Manufacturing Electrochromic Tungsten Oxide Films

A new and simple method for the preparation of electrochromic tungsten oxide film is presented. This novel approach can be realized by introducing a nanoporous textured polyacrylic acid (PAA) layer between tungsten oxide layer and indium tin oxide (ITO) one by dip-coating process. Homogeneous film with a thickness of about 0.8 μm is made by single dipping a PAA-coated ITO glass in the WO3-NH4OH solution and shows an X-ray amorphous structure. During the cathodic and anodic processes by chronopotentiometry, the present films exhibit highly reversible electrochemical insertion of lithium ions; the corresponding inserted charge of 12.5 mC/cm2gives rise to a marked blue color yielding the change in optical density (AOD) of 0.65 at 550 nm and a coloration efficiency(η)of 51.8 cm2/C.

Lithium Intercalation in Nanoporous Anatase TiO2 Studied with XPS

Intercalation of lithium ions in nanoporous anatase TiO2 was studied with XPS using a novel electrochemical preparation technique. The electrolyte was 0.5 M LiClO4 in acetonitrile (not water-free). The electrochemical insertion of lithium ions creates reduced Ti ions (Ti3+), which was observed as a new well-resolved state in the Ti 2p core level spectrum shifted 2.1 eV to lower binding energy. The new Ti 2p state was reversible when the electrode was deintercalated. Changes in the O 1s core spectra were also observed and discussed in terms of hydrated lithium ions in the Helmholtz layer, or formation of Li2O/LiOH.

MVO5(M = Nb, Ta) mixed oxides: sol–gel synthesis, structural and thermal characterization and electrochemical Li+insertion

Our studies on the preparation, via the sol–gel techniques, of MVO5(M = Nb, Ta) oxides have been rewarded here with an increased understanding of the synthesis process. The sol–gel method is at the moment the only procedure for producing NbVO5 as a pure phase. We present results concerning the influences of different parameters on the nature of the final products in the V–Nb–O system. Compounds NbVO5 and TaVO5 are isostructural with orthorhombic unit cells. The structural parameters have been refined using the Rietveld method with space group Pnma. Thermal analyses of the precursor xerogels show that the thermal effects depend on the nature of the M cations. The crystallization and decomposition temperatures are lower for NbVO5 than for TaVO5. The electrochemical insertion of lithium ions into the new MVO5(M = Nb, Ta) mixed oxides has also been investigated. For both materials, this process is complex and consists of three main steps. The maximum insertion degrees (x in LixMVO5) achieved after the reduction process are x= 1.95 for NbVO5 and x= 1.57 for TaVO5. The galvanostatic cycling studies show the good rechargeability of the Li+/e– insertion/deinsertion process in the MVO5 oxides.

Lithium insertion into vanadium oxide bronze containing nickel

Electrochemical insertion of lithium ions into V 2O 5 bronze containing nickel (NiV 2O 5, Ni V = 0.075 ) was studied by comparing with V 2O 5. The difference in the amount of lithium inserted up to the second plateau was about 0.15 between NiV 2O 5 and V 2O 5 on open circuit voltage (OCV) curves. The broadened reduction and oxidation peaks in cyclic voltammogram, indistinct plateaux in discharge curve, and wide gap between OCV and discharge potential observed on NiV 2O 5 suggested that nickel ions in the bronze are placed in the same sites as lithium and disturb lithium diffusion along the channels of V 2O 5 structure. The present results implied that two factors, charge balance and lattice sites, governed the insertion of foreign ions, such as Li + and Ni 2+, into V 2O 5 lattice.