Positive Electrode In Lithium Batteries Research Articles

Corrosion processes in battery systems based on non-aqueous electrolytes (a review)

The article presents some new results of the studies of corrosion processes in lithium battery systems with non-aqueous electrolytes. The following processes are considered: electrochemical corrosion of positive and negative electrodes, corrosion of structural materials, and electrochemical and chemical decomposition of non-aqueous electrolytes, which occurs simultaneously with the main electrochemical process. The main attention is paid to the role of corrosion processes on current collectors of current sources. Corrosion processes on aluminum current collector and stainless steel current collector for positive electrodes of lithium batteries are particularly considered. An important role of corrosion in the degradation of the lithium battery is emphasized. Case studies on corrosion in positive electrodes and lithium electrode are mentioned. Considerable attention is paid to the contact corrosion in aircraft, with an emphasis on the need for further studies of this process. The proposed corrosion mechanisms are considered.

Ab initio calculations of structural and electronic properties of WSe2 compound

The transition-metal dichalcogenides (TMDC) attracted a lot of attention for a variety of applications and more particularly as positive electrodes in lithium batteries. Among these materials the most intensively studied, we find semiconductors such as tungsten diselenide WSe2.In this work, we have perform first-principle calculations to investigate the structural and electronic properties of WSe2 compound, using the density functional theory DFT within the full-potential linearized augmented plane wave method (FP-LAPW) implemented in the code WIEN2k.The Generalized Gradient Approximation (GGA) as proposed by Perdew et al. was used to describe the exchange–correlation potential; and so to obtain the structural properties to assess the equilibrium lattice, the total energy of the system for different values of the primitive mesh and determining the volume at equilibrium, the compressibility modulus and the energy of the ground state, which are close to experimental results reported in the literature.The electronic properties were obtained by calculating the band structure and the density of state ″DOS″, by using three approaches: Local Density Approximation (LDA), Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ). The calculated energy bands indicate the semiconductor behavior of WSe2 with an indirect band gap of 0.9 eV using LDA, of 1 eV with GGA and 1.18 eV by mBJ. This last band gap value is the closest of the experimental result of 1.2 eV.

Synergistic Effect of Innovating Electrode Technology and Eddy-Current Electromagnetic Impedance for Non-Destructive Testing are Resulting in Increasing Battery Power

The value of contact resistance between metallic current lead and electrode mass composite is one of the key parameters for determination of performance of energy storage devices, such as batteries, supercapacitors, etc. During discharge process of batteries the resistance of interface between electrode mass layer & the current collector influences on the battery voltage The surface of the aluminum foil, which used as a current collector for positive electrodes in lithium batteries is passivated by Al2O3 film that has a low electric conductivity. As result the energy and power battery are decreased. Our article is connected with technology for Li electrode production that insures the low interface resistance between electrode collector and electrode mass, the increasing the power of batteries, and stability the cycling. We have the strong opinion that the success of technology must be supported by nondestructive testing the initial materials, semi- and final product during batteries production.

Effect of Nature of Polymer Binder on the Properties of Conductive Protective Coatings for Current Collectors of Positive Electrodes of Lithium Batteries

Effect of Nature of Polymer Binder on the Properties of Conductive Protective Coatings for Current Collectors of Positive Electrodes of Lithium Batteries

Synthesis and electrochemical performance of Li2VxMn1−xO3 positive electrode for lithium batteries

Lithium excess manganese oxide, namely, Li2MnO3 is under investigations to improve its electrochemical performance as the next generation high capacity electrode material. Partial substitution of Mn by another metal is one of the ways to influence the properties of Li2MnO3. In the present study, vanadium is used to partially substitute Mn in various ratios. Li2VxMn1−xO3 (x = 0.1, 0.2, 0.3 and 0.4) samples are prepared by sol–gel method using stoichiometric ratios weights of Mn(CH3COO)2·4H2O, Li2CO3 and NH4VO3. The crystalline phases are identified by X-ray diffraction. The particles morphology is studied with a scanning electron microscope. Furthermore, impedance measurements (EIS) are applied using frequency range between 106 and 10−2 Hz. The optimum EIS is obtained with for the Li2V0.3Mn0.7O3 cell. Cyclic voltammetric measurements are carried out for the lithium manganate materials between 0.01 and 4.5 V versus Li+ with scan rate 0.1 mV s−1. Also, galvanostatic charging and discharging cycling of the cells are achieved with the same potentials windows using charging and discharging current intensity of 10 mA g−1 between 1.5 and 4.5 V versus Li+. It is observed that Li/Li2V0.3Mn0.7O3 cell has higher specific discharge capacity, 227 mAh g−1 rather than the other cells.

Synthesis and Caracterization of Mesoporous FePO4 as Positive Electrode Materials for Lithium Batteries

Mesoporous iron phosphates were synthesized using sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) as surfactants. The material synthesized in the presence of SDS was not applied as a positive electrode active material of a lithium battery. The results show that the obtained FePO4 has a mesoporous structure with a specific surface area of 70 m2 g−1 and a dominant pore diameter of 3 nm. Those mesoporous were characterized by different microstructural and electrochemical analyzes. Among the materials studied under different conditions, those calcined at 450°C preserve mesoporous structures and exhibit the best electrochemical performance when used as active materials of the positive electrodes of lithium batteries. Effectively, a relatively high specific capacity of 135 and 122 mAh g−1 was registered at C/20 collected experimentally by the samples synthesized in the presence of SDS and CTAB, respectively.

Olivine-Based Blends As Positive Electrodes for Lithium Batteries

Blended cathode materials made by mixing LiFePO4 (LFP) with LiMnPO4 (LMP) or LiNi1/3Mn1/3Co1/3O2 (NMC) that exhibit either high specific energy and high rate capability were investigated. The layered blend LMP-LFP and the physically mixed blend NMC-LFP are evaluated in term of particle morphology and electrochemical performance. Results indicate that the LMP-LFP (66:33) blend has better discharge rate than the LiMn1-yFeyPO4 with the same composition (y=0.33) and NMC-LFP (70:30) delivers a remarkable stable capacity over 125 cycles. Finally, in situ voltage measurement methods were applied for the evaluation of the phase evolution of blended cathodes and gradual changes in cell behaviour upon cycling.

Olivine-Based Blended Compounds as Positive Electrodes for Lithium Batteries

Blended cathode materials made by mixing LiFePO4 (LFP) with LiMnPO4 (LMP) or LiNi1/3Mn1/3Co1/3O2 (NMC) that exhibit either high specific energy and high rate capability were investigated. The layered blend LMP–LFP and the physically mixed blend NMC–LFP are evaluated in terms of particle morphology and electrochemical performance. Results indicate that the LMP–LFP (66:33) blend has a better discharge rate than the LiMn1−yFeyPO4 with the same composition (y = 0.33), and NMC–LFP (70:30) delivers a remarkable stable capacity over 125 cycles. Finally, in situ voltage measurement methods were applied for the evaluation of the phase evolution of blended cathodes and gradual changes in cell behavior upon cycling. We also discuss through these examples the promising development of blends as future electrodes for new generations of Li-ion batteries.

Structural and electronic studies of metal hexacyanoferrates based cathodes for Li rechargeable batteries

Operando XANES and EXAFS spectra on the newly prepared Fe hexacyanocobaltate active material for positive electrodes in lithium batteries have been recorded at the XAFS beamline of Elettra using a suitable in situ cell. In this way, it was possible to follow in detail the main structural and electronic changes during the charge and discharge processes of the battery. The use of a chemometric approach for data analysis is also underlined.

Studies of Aluminum-Doped LiNi0.5Co0.2Mn0.3O2: Electrochemical Behavior, Aging, Structural Transformations, and Thermal Characteristics

This paper is dedicated to studies of the electrochemical behavior, the structural and thermal features of the Ni-rich LiNi0.5Co0.2Mn0.3O2 undoped and Al-doped (∼0.01 at.%) materials for positive electrodes of lithium batteries. We have found that structural characteristics of these materials are quite similar from the crystallographic point of view. It was demonstrated that Al substitution in the doped LiNi0.5Co0.2Mn0.3O2 is preferred at Ni sites over Co sites, and the thermodynamic preference for Al3+ substitutions follows the order: Ni>Co>Mn. The lower capacity fading of the Al-doped electrodes upon cycling and aging of the cells in a charged state (4.3 V) at 60°C, as well as more stable mean voltage behavior, are likely due to the chemical and structural modifications of the electrode/solution interface. The Al-doped LiNi0.5Co0.2Mn0.3O2 electrodes demonstrate also lower resistances of the surface film and charge-transfer as well as lower activation energies for the discharge process. From XPS studies we conclude that the modified stable and less resistive interface on the Al-doped particles comprises the Li+-ion conducting nano-sized centers like LiAlO2, AlF3, etc., which promote, to some extent, the Li+ ionic transport to the bulk. A partial layered-to-spinel transformation was established upon cycling of LiNi0.5Co0.2Mn0.3O2 cathodes.

Fabrication and electrochemical characterization of amorphous lithium iron silicate thin films as positive electrodes for lithium batteries

In this work we reported, for the first time, the preparation by radio frequency sputtering and the electrochemical characterization of Li/M/Si/O thin films (M = Fe, Mn), as positive electrodes for lithium microbatteries. The deposited films were amorphous both in case of pure iron and mixed iron/manganese compositions. The electrochemical performances, in terms of capacity values and coulombic efficiency, were comparable to those currently reported for the corresponding crystalline bulk materials. In particular, capacities of the order of 50 mAh g−1 were obtained at 2.5 C with coulombic efficiency near 90% by using a standard liquid electrolyte. Our preliminary electrochemical results, together with the easiness of preparation, suggested that Li/M/Si/O thin films could be interesting candidates as cathodes in lithium microbatteries.

Function-oriented design of conjugated carbonyl compound electrodes for high energy lithium batteries

Organic carbonyl compounds are potentially low-cost, sustainable, and high energy density electrode materials, but are plagued by unsatisfactory active-site utilization, low discharge potentials and low rate discharge–charge performance in battery applications. We herein disclose a function-oriented design of carbonyl compounds with multi-electron reactions as positive electrode materials for rechargeable lithium batteries, showing that molecular orbital profiles and energetics can be applied for the prediction of carbonyl utilization and modulation of redox potentials. By embedding pre-aromatic 1,2-dicarbonyl moieties in the extended conjugated systems, the desirable molecules integrate all known stabilizing factors and enable full four-Li uptake. Remarkably, two new carbonyl electrodes, pyrene-4,5,9,10-tetraone and 1,10-phenanthroline-5,6-dione, deliver a reversible capacity of 360 mA h g−1 and an average working potential of 2.74 V, respectively, providing insights in designing high-energy organic positive electrodes of lithium batteries for efficient energy storage and conversion.

Structural Study of the LiyNa1-yMnFe2(PO4)3(y = 0, 0.5, 0.75) Alluaudite Phases and Their Electrochemical Properties as Positive Electrode in Lithium Batteries

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ChemInform Abstract: Structural Study of the Li0.5Na0.5MnFe2(PO4)3 and Li0.75Na0.25MnFe2 (PO4)3 Alluaudite Phases and Their Electrochemical Properties as Positive Electrodes in Lithium Batteries.

AbstractLixNa1‐xMnFe2(PO4)3 (x = 0, 0.5, 0.75) is synthesized by a sol—gel method from stoichiometric amounts of Na2CO3, Li2CO3, MnCO3, FeC2O4, and (NH4)H2PO4 in H2O containing HNO3 and citric acid (800 °C, 30 min).

Structural Study of the Li0.5Na0.5MnFe2(PO4)3 and Li0.75Na0.25MnFe2(PO4)3 Alluaudite Phases and Their Electrochemical Properties As Positive Electrodes in Lithium Batteries

The alluaudite lithiated phases Li(0.5)Na(0.5)MnFe(2)(PO(4))(3) and Li(0.75)Na(0.25)MnFe(2)(PO(4))(3) were prepared via a sol-gel synthesis, leading to powders with spongy characteristics. The Rietveld refinement of the X-ray and neutron diffraction data coupled with ab initio calculations allowed us for the first time to accurately localize the lithium ions in the alluaudite structure. Actually, the lithium ions are localized in the A(1) and A(1)' sites of the tunnel. Mössbauer measurements showed the presence of some Fe(2+) that decreased with increasing Li content. Neutron diffraction revealed the presence of a partial Mn/Fe exchange between the two transition metal sites that shows clearly that the oxidation state of the element is fixed by the type of occupied site. The electrochemical properties of the two phases were studied as positive electrodes in lithium batteries in the 4.5-1.5 V potential window, but they exhibit smaller electrochemical reversible capacity compared with the non-lithiated NaMnFe(2)(PO(4))(3). The possibility of Na(+)/Li(+) ion deintercalation from (Na,Li)MnFe(2)(PO(4))(3) was also investigated by DFT+U calculations.

Study of a Layered Iron(III) Phosphate Phase Na3Fe3 ( PO4 ) 4 Used as Positive Electrode in Lithium Batteries

The layered phase prepared by solid-state reaction was studied as positive electrode in lithium batteries. Up to 1.9 ions/f.u. could be intercalated, and only 1.7 ions could be extracted between 4.5 and 2 V vs with an average voltage of around . In situ and ex situ X-ray diffraction data and Mössbauer spectroscopy measurements indicate that the intercalation/deintercalation process occurs through a solid solution process and is reversible. To improve its electrochemical performances, was also prepared via a hydrothermal method that leads to a significant particle size reduction. However, no clear improvements of the cycling performances were observed using this material as positive electrode in sodium and lithium batteries.

On the room temperature synthesis of monoclinic Li 3FeF 6: A new cathode material for rechargeable lithium batteries

The α-polymorph of Li 3FeF 6 has been obtained at room temperature by a precipitation reaction from aqueous solution. This easy procedure that does not require any further annealing at high temperature yields a white powder with particles sizes ranging from 250 to 400 nm. After proper processing by mechanical milling, particle sizes clearly below 100 nm are achieved and this fluoride reacts reversibly with lithium at an average voltage of 3.1 V, which is expected for the Fe 3+/Fe 2+ redox couple. After 12 h of ball milling observed average particle size is ca. 50 nm and a reversible capacity of 100 mA h g −1 is obtained. This corresponds to 70% of the theoretical capacity expected for the one electron reduction of Fe 3+. The mentioned capacity is fairly kept upon cycling making the new material useful as the positive electrode in lithium batteries. This is the very first time that a material for cathode application in lithium batteries is prepared at room temperature and from aqueous solution, a procedure which is easily scalable and hence of high industrial interest.

Polymorphism and structural defects in Li2FeSiO4

Li(2)FeSiO(4), an interesting material with potential applications as the positive electrode in lithium batteries, shows complex crystal chemistry due to the versatility of cation ordering (Li(+), Fe(2+), Si(4+)) within tetrahedral sites of buckled hexagonal close packed layers of oxygen atoms. This study, conducted through X-ray and electron diffraction experiments, focuses on three samples of Li(2)FeSiO(4) (obtained from ceramic synthesis at 700 degrees C, 800 degrees C and 900 degrees C) which may contain significant amounts of structural defects. Two polymorphs of Li(2)FeSiO(4) were isolated and investigated through X-ray diffraction and electron microscopy. A new form of Li(2)FeSiO(4) (space group Pmnb with a = 6.2853(5), b = 10.6592(8) A and c = 5.0367(4) A or alternatively P2(1)/n with a = 6.2819(1) A, b = 10.6575(2) A, c = 5.0371(1) A, beta = 90.032(7) degrees ) prepared at 900 degrees C, shows cooperative small displacements of lithium cations from one tetrahedral site (up) to another (down). Attempts to prepare the second, low-temperature, polymorph (space group P2(1)/n, a = 8.2253(5) A, b = 5.0220(1) A, c = 8.2381(4) A, beta = 99.230(2) degrees ) previously reported by Nishimura et al., lead to crystals exempt of structural defects (at 700 degrees C) or built up by an intergrowth between the low temperature polymorph and a residue of the high temperature one.

Structural and Electrochemical Characterization of Composite Layered-Spinel Electrodes Containing Ni and Mn for Li-Ion Batteries

The structural features of a series of intergrown “layered-spinel” composite materials with initial formulation , previously shown to have attractive properties as positive electrodes in lithium batteries, were studied. The existence of a layered and a spinel component in samples with was confirmed by both X-ray diffraction and magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The unit-cell volume of the layered component was shown to decrease as a function of , while the unit-cell parameter of the cubic spinel phase did not vary significantly. The MAS NMR spectra confirmed that the cation distribution in these layered-spinel composite structures is extremely complex; analysis of the data, particularly for intermediate values of , suggested that , , , and ions are present, rather than just and as implied by the ideal formula . The structural changes induced by the electrochemical removal and reinsertion of lithium in the composite electrode for were followed by MAS NMR and related to the different signatures in the composition-voltage profiles. The activity of both the layered and the spinel component within a 5–2 V voltage window was confirmed.

Dual functioned BiOF-coated Li[Li0.1Al0.05Mn1.85]O4 for lithium batteries

Spinel-type lithium manganese oxides have shown considerable promise for the positive electrode in lithium batteries but have suffered from poor performance at high temperatures (40–60 °C). The electrochemical properties of BiOF-coated spinel Li[Li0.1Al0.05Mn1.85]O4 at elevated temperatures (55 °C) were investigated. BiOF nanoparticles were well coated on spinel Li[Li0.1Al0.05Mn1.85]O4, as confirmed by scanning and transmission electron microscopy. The BiOF-coated spinel Li[Li0.1Al0.05Mn1.85]O4 electrode had excellent capacity retention at 55 °C, maintaining its initial discharge capacity of 96.1% after 100 cycles. This improved cycling performance was ascribed to the presence of the BiOF layer on the spinel particles, which prevented the infiltration of HF generated by the decomposition of electrolytic salt, LiPF6, in the electrolyte. This property resulted in a considerable reduction of manganese dissolution of the BiOF-coated spinel Li[Li0.1Al0.05Mn1.85]O4. Transmission electron microscopy of extensively cycled particles confirmed that the particle surface of the BiOF-coated Li[Li0.1Al0.05Mn1.85]O4 remained almost completely undamaged, whereas pristine spinel particles were severely deteriorated. In the present paper, we have tried to understand the role of the BiOF coating layer and why such coatings resulted in better battery performances, using BiOF-coated Li[Li0.1Al0.05Mn1.85]O4. The BiOF coating layer on the surface of Li[Li0.1Al0.05Mn1.85]O4 particles can be defined as follows; the oxyfluoride layer provides a strong protecting layer against HF attack and scavenges HF, thus resulting in reducing HF from the electrolyte. Synergistically, these actions resulted in the significantly improved high temperature cycling performances exhibited by the BiOF-coated Li[Li0.1Al0.05Mn1.85]O4.