Lithium Corrosion Research Articles

Effects of nonionic surfactant on the parasitic corrosion of lithium anode in lithium–water battery

The use of a nonionic surfactant, namely cocamide diethanol amine (CDA), as a parasitic inhibitor for lithium corrosion in 4.0 M LiOH aqueous solution has been evaluated in the 298–313 K temperature range.

Understanding the Influence of Structure on Activity and Stability in the Catalysis of the Oxygen Evolution Reaction (OER) Using Crystalline Oxides As a Platform

Oxides of manganese and cobalt have proved to be effective (electro)catalysts for the water oxidation half-reaction in water splitting. Recently, the research focus has mostly been on developing high surface area morphologies of catalysts with high specific activity that are potentially easily adaptable to photoelectrochemical cells for water splitting. However, it is still not completely understood why these catalysts show such high intrinsic activity, and many have amorphous structures, making it difficult to elucidate structure-function relationships. Using crystalline oxides as an experimental framework, we have elucidated the effects of structure on the activity and stability of cobalt and manganese oxides for the oxygen evolution reaction (OER). For instance, in two distinct polymorphs of lithium cobalt oxide (LiCoO2), we have found the cubic structure (Fd-3m, spinel-like), with a Co4O4 oxo-metallic cube motif, is highly active for water oxidation, whereas the layered polymorph (R-3m) with slabs of CoO2 (used for rechargeable Li ion batteries) is not. In fact, upon electrochemical processing, the layered polymorph undergoes a surface restructuring that we can monitor using high-resolution transmission electron microscopy (HRTEM). This has been shown to occur in both aqueous and non-aqueous electrolyte. After the transformation occurs, which can also be monitored by the electrochemical profile and corrosion of lithium, the OER activity of the layered material mirrors that of the cubic LiCoO2. However, it is unstable and eventually diminishes with repeated electrochemical cycling or prolonged electrolysis. In this way, we show that the underlying bulk crystal structure has influence over not just activity, but also stability, both equally important for commercial applications. Parallel to this work, we isolated discrete Co2O2, Co3O3, and Co4O4 molecular clusters in the same ligand sets, and found only the complete Co4O4 cubanes were catalytically active for water oxidation. This difference in activity correlates to the accessibility of a formal Co4+ oxidation state, which occurs at modest potentials only for the cubane, which compensates by delocalizing the hole across all cobalt and bridging oxos. The singly oxidized cubane is sufficient to produce O2 just in reaction with hydroxide. We believe this phenomenon relates back to the solid-state, and is in part the reason for the high activity in the cubic LiCoO2.

Electrochemical in situ investigations of SEI and dendrite formation on the lithium metal anode.

This comparative work studies the self-enforcing heterogeneity of lithium deposition and dissolution as the cause for dendrite formation on the lithium metal anode in various liquid organic solvent based electrolytes. In addition, the ongoing lithium corrosion, its rate and thus the passivating quality of the SEI are investigated in self-discharge measurements. The behavior of the lithium anode is characterized in two carbonate-based standard electrolytes, 1 M LiPF6 in EC/DEC (3 : 7) and 1 M LiPF6 in EC/DMC (1 : 1), and in two alternative electrolytes 1 M LiPF6 in TEGDME and 1 M LiTFSI in DMSO, which have been proposed in the literature as promising electrolytes for lithium metal batteries, more specifically for lithium/air batteries. As a result, electrolyte decomposition, SEI and dendrite formation at the lithium electrode as well as their mutual influences are understood in the development of overpotentials, surface resistances and lithium electrode surface morphologies in subsequent lithium deposition and dissolution processes. A general model of different stages of these processes could be elaborated.

Electrolytes for lithium and lithium ion batteries: From synthesis of novel lithium borates and ionic liquids to development of novel measurement methods

Abstract This review covers various aspects of electrolyte investigations. The first section reports on synthesis and characterization of lithium salts and ionic liquids, including some unpublished recent work. The next part is devoted to transference number measurements of lithium ions. It contains recently published work and new results on this rarely investigated but important topic. Studies of anodic aluminum dissolution with our novel fast impedance scanning electrochemical quartz microbalance (FIS-EQCM) follow next. After a short introduction to the method, some recently published results are reviewed along with some yet unpublished material. We have also shown that the solubility of solids and gases in liquids can be measured with this equipment, including the solubility of lithium salts in ionic liquids. First results of FIS-EQCM studies show that electroplating and corrosion of lithium and subsequent dissolution of the SEI can be studied as well. The last parts of this manuscript are dedicated to the investigation of miscellaneous topics that are of interest for studies of electrolytes for LIBs.

Electrochemical Performance of Ionic Liquids with Bis(trifluorosulfonyl)Imide Anion for Lithium-Ion Battery Application

Room temperature ionic liquids (RTILs) formed from bulky cations and anions have attracted significant attention as potential electrolyte components for the next generation of lithium-ion batteries. Unfortunately, the lithium–ion batteries fabricated with neat ILs as electrolytes possess low ionic conductivity and lithium corrosion problems. Both surface-active and ionic IL additives have been used overtime to improve the electrochemical performance.a Bis(trifluoromethylsulfonyl)imide (TFSI-) - based ionic liquids (Fig.1) are known to have low cathodic reduction potentials at graphite electrodes that affect formation of protective layer on solid electrolyte interface (SEI)b. On the contrary, at metal electrodes including lithium, TFSI- anions favor electrolyte reduction which is due to stabilization of LiTFSI ion pair formed under reducing conditions in presence of lithium cations and TFSI anions.Compared to other lithium salts as IL ionic additives, such as LiBF4 and LiTFSI, lithium hexafluorophosphate (LiPF6) demonstrated an improved electrochemical cathodic behavior. Furthermore, the presence and concentration of a lithium salt have an influence on the cathodic potential electrochemical window. For example, addition of LiPF6 to a neat solution of 1-butyl-2,3-dimethyl-imidazolium bis(fluoromethyl-sulfonyl)imide (FSI) has been shown to change the cathodic electrochemical window from -2.8 to -4.10V.c Present study is focused on electrochemical performance evaluation of ionic liquids, specifically 1-ethyl-3 methylimidazolium (EMIM TFSI) and 1-butyl-1-methylpyrrolidonium (PYR14 TFSI) (Fig.1) in symmetrical cells with two lithium metal electrodes and CelgardTM separator.The results for symmetrical coin cells (CR2025) constructed with lithium disks deposited onto 0.5mm spacers and separated by CelgardTM 20mm polyethylene membrane with 12 mL of ionic liquid on each side of the separation membrane will be presented. The electrochemical performance of the symmetrical cells will be compared with the results obtained for the half-cells with the earlier developed silicon-based working electrode. EMIM TFSI and PYR14 TFSI ionic liquids in presence and absence of LiPF6 for symmetrical cells and half-cells will be discussed in terms of coin cell performance, impedance, chemical transformations, and changes to the morphology that take place during cell storage, solid electrolyte interface (SEI) formation, and charge-discharge cycling. NMR study of the ionic liquids will be addressed to study the dynamics of the cations, anions, and ion pairs in presence and absence of ionic additive LiPF6. Pulsed field gradient NMR is used to determine self-diffusion coefficients of 1H and 19F.REFERENCES: a J. Xiang, F. Wu, R. Chen, L.Li, H. Yu, J. of Power Sources, 233, 115 (2013) b Y. Katayama, T. Morita, M. Yamagata, and T. Miura, Electrochemistry (Tokyo, Jpn.), 71, 1033 (2003) c A. S. Best, A. I. Bhatt, and A.F. Hollendamp, J. of the electrochemical Society, 157 (8) A903-A911 (2010)

Overview of the vanadium alloy researches for fusion reactors

Various vanadium alloys are being developed as one of the options of structural materials for advanced blankets of fusion reactors. Besides the large heats made in Japan and US, a 110kg V–4Cr–4Ti ingot was produced in RF recently. Development of advanced vanadium alloys were also carried out, such as the ultra-fine grain alloys containing Y and that with W and TiC strengthening particles. Investigations were performed for further widening of temperature and mechanical application windows of the reference V–4Cr–4Ti alloy by plastic deformation and heat treatments. Neutron irradiation effects combined with lithium corrosion were studied. In addition, some efforts are oriented to issues related to DEMO blanket manufacturing technology, such as W coating for first wall protection and the welding technologies to fabricate large vanadium component. This paper highlights the recent activities of these vanadium alloy researches, discusses the critical issues and summarizes the remaining issues to be addressed.

Modeling self-discharge of Li/SOCl 2 cells

A kinetic expression for the chemical reaction of lithium metal with thionyl chloride is presented that is consistent with calorimetric measurements of the heat generation from a thionyl chloride cell. The kinetics expression is incorporated into a well-established electrochemical model for the discharge behavior, and then used to estimate the life of the battery under an intermittent discharge so as to assess the importance of lithium corrosion. The model predicts that, under the conditions examined, there is no danger of depleting the lithium anode and so introducing a safety hazard.

Main aging mechanisms in Li ion batteries

Some of the aging mechanisms occurring in Li ion batteries, either on rest or on cycling, are described from long-term storage or cycling data. Generally, the most critical part of the cell is the negative electrode/electrolyte interface. Stability of the solid electrolyte interface (SEI), more generally of the passivating layer, must be insured by proper material choice and additives. Excessive growth induces with time a capacity loss corresponding to the lithium corrosion, and a reduction of power capability of the electrode, from the active surface area degradation. In a worst case, reduction of charge rate capability may lead to local lithium plating during cycling, strongly aggravating the capacity fading. When the SEI is correctly built, with low electronic conductivity, the negative electrode stability can be very stable, as described by long-term aging (more than 4 years) at higher temperature than ambient. Vinylen carbonate is confirmed as outstanding additive. At elevated temperature, high SOC induces side reactions at the positive interface, involving electrolyte components oxidation. The results are an increase of cell impedance, and possible slow CO 2 evolution. Presence of lithium carbonate greatly enhanced the gas formation. The observed impedance increase indicates a reduction of the active surface area, in agreement with solid deposit. When properly designed with an appropriate choice of active materials and electrolyte, the Li ion system can provide a very long service.

A capacity and power fade study of Li-ion cells during life cycle testing

We tested three lithium-ion cells to evaluate capacity and power fade during cycle life testing of a hybrid electric vehicle (HEV) cell with varying state of charge (ΔSOC). Test results showed that the cells had sufficient power and energy capability to meet the Partnership for a New Generation of Vehicles (PNGV), now called FreedomCAR, goals for Power Assist at the beginning of life and after 120,000 life cycles using 48 cells. The initial static capacity tests showed that the capacity of the cells stabilized after three discharges at an average of 14.67 Ah. Capacity faded as expected over the course of 120,000 life cycles. However, capacity fade did not vary with ΔSOC. The hybrid pulse power characterization (HPPC) tests indicated that the cells were able to meet the power and energy goals at the beginning of testing and after 120,000 life cycles. The rate of power fade of the lithium-ion cells during cycle life testing increased with increasing ΔSOC. Capacity fade is believed to be due to lithium corrosion at the anode, and power fade suggested a buildup of the SEI layer or a decrepitation of the active material.

Corrosion of Refractory Alloys in Molten Lithium and Lithium Chloride

Several refractory materials have been considered over the years as containment material for lithium and lithium halides. Surface modified refractory metals are being extensively investigated for containment of reactive metals, radionuclides and their compounds. An overview of experimental observations and results of liquid lithium corrosion of selected engineering refractory materials are presented. The nature of the degradation and its mechanism has been explained. The influence of temperature, microstructure, stress, impurities and service time on the corrosion behavior for various refractory alloys have been discussed. Selection rules for materials of containment for liquid lithium and lithium compounds have been suggested. Recent experimental observations on the behavior of tantalum and niobium-based refractory metal alloys in a specific molten salt environment comprising LiCl/Li2O/Li/Li3N at 725°C have been included in an effort to select suitable materials for molten salt equipment. It has been observed that oxygen contamination is particularly harmful for the refractory metal alloys where as nitrogen is deleterious to iron-based alloys.

Corrosion of Refractory Alloys in Molten Lithium and Lithium Chloride

Several refractory materials have been considered over the years as containment material for lithium and lithium halides. Surface modified refractory metals are being extensively investigated for containment of reactive metals, radionuclides and their compounds. An overview of experimental observations and results of liquid lithium corrosion of selected engineering refractory materials are presented. The nature of the degradation and its mechanism has been explained. The influence of temperature, microstructure, stress, impurities and service time on the corrosion behavior for various refractory alloys have been discussed. Selection rules for materials of containment for liquid lithium and lithium compounds have been suggested. Recent experimental observations on the behavior of tantalum and niobium-based refractory metal alloys in a specific molten salt environment comprising LiCl/Li2O/Li/Li3N at 725°C have been included in an effort to select suitable materials for molten salt equipment. It has been observed that oxygen contamination is particularly harmful for the refractory metal alloys where as nitrogen is deleterious to iron-based alloys.

Contrasting film formation reactions of ethereal and carbonate solvents on metallic lithium

A summary of studies by photoelectron spectroscopy of the reactions of prototypical ethereal and alkyl carbonate solvents with lithium metal in ultra-high vacuum (UHV) is presented. The Li/solvent interface is formed by condensing solvent vapor onto the surface of freshly vacuum evaporated Li at 130 K. The reaction is observed by obtaining core-level photoelectron spectra as a function of temperature. The interfacial reactions are distinctly different for the ethereal vs. the carbonate solvents. The ethers, both cyclic (THF and 1,3-dioxolane) and linear (glymes), react initially to form an LiOR or radical anion (1,3-dioxolane) precursor, followed by the formation of a polyether layer. In the carbonates, there is a significant difference between linear and cyclical forms. The linear carbonates (DMC and DEC) are more reactive, reacting even below the melting point, and produce both LiOCO 2R and LiR (alkyl lithium). There are no unreacted solvent molecules left on the surface at room temperature. Since alkyl lithium is soluble in the bulk solvent, the lithium surface will not passivate in this solvent until considerable dissolution of lithium has occurred. The cyclic carbonate PC forms only insoluble LiOCO 2R, but no unreacted PC (or PC-like molecule) remains at room temperature. Thus, the corrosion of lithium in DMC/DEC is predicted to be significantly greater than in PC. Since the ethers incorporate a significant amount of solvent molecule in the passive layer, e.g. by polymerization, the SEI layer formed in the ethers is predicted to be more highly conducting than in the carbonates. This prediction is based on the chemistry of the pure solvent molecules, absent real life impurities, e.g. water, or an anion, which may react preferentially with lithium.

Corrosion performance of ferrous and refractory metals in molten salts under reducing conditions

A lithium reduction technique to condition spent fuel for disposal has been developed at the Argonne National Laboratory. There is a need to ensure adequate vessel longevity through corrosion testing and, if necessary, materials development. Several ferrous alloys and tantalum specimens were submitted to a corrosion test at 725 °C for thirty days in an argon atmosphere, using a lithium-chloride salt saturated with lithium metal and containing small amounts of lithium oxide and lithium nitride. The samples did not show dimensional or weight change, nor could corrosion attack be detected metallographically. The lithium-saturated salt system did not show any behavior similar to that of liquid lithium corrosion. From testing in other gas compositions, it appears that the presence of oxygen in the system is necessary to produce severe corrosion.

Ion–ion interactions and lithium stability in a crosslinked PEO containing lithium salts

The electrochemical properties of a solid polymer electrolyte prepared by chemical crosslinking of PEO 2000 and containing LiAsF 6 or LiCF 3SO 3 were investigated for electrochemical window, lithium stability and lithium/electrolyte interface stability. FTIR spectroscopy of the salt anion (AsF 6 − and CF 3SO 3 −) was also used to determine the nature and the extent of ion pairing and ion aggregation in these crosslinked electrolytes. The lithium corrosion appears as a diffusion limited process as the coulombic efficiency of a lithium deposit decreases with the square root of the contact time of lithium with the crosslinked PEO. Impedance parameters are consistent with an increase of the passivating layer upon storage. Their values strongly differ with the salt anion.

The Li/Li+ couple in propylene carbonate electrolytes and poly(methyl methacrylate) gels

Kinetics and mechanisms for the electrodeposition of lithium from propylene carbonate and PMMA gelled electrolytes were studied using chronoamperometric, cyclic voltammetric and chronopotentiometric methods at a nickel microelectrode. Nucleation and crystal growth models have been proposed for three salt systems. Exchange current densities, coulombic stripping efficiencies and lithium corrosion rates were evaluated.

The lithium/polymer electrolyte interface

Kinetics and mechanisms for the electrodeposition of lithium from liquid and solid polymer electrolytes formed from lithium salts or from lithium salt complexes have been studied using chronoamperometric and cyclic voltammetric methods at a microelectrode. The type of nucleation and crystal growth process was determined as a function of polymer electrolyte composition. Exchange current densities, coulombic stripping efficiencies and lithium corrosion rates were evaluated.

Lithium-cycling efficiency in inorganic electrolyte solution

Lithium-cycling efficiencies and corrosion rates were measured in half cells. The elaborated inorganic electrolyte solution, consisting mainly of LiAlCl 4 and SO 2, has a conductivity of 2.2 mS/cm at −25 °C and 98 mS/cm at 60 °C. Lithium-cycling efficiencies of about 98% at 40 mA/cm 2 for at least 50 cycles were achieved. Depending on improved electrolyte preparation, the current density for the lithium corrosion could be reduced from 12.1 to 6.5 μA/cm 2. The results indicate stability, compatibility and high rate capability of the system lithium/inorganic electrolyte solution.

The Corrosion Behavior of Fe-Ni-Cr Alloys in Liquid Lithium

The corrosion behavior of several Fe-Ni-Cr alloys in static liquid lithium are reported in this paper. The alloys were 316SS, Ti-modified 316SS, HR-1, low activity HT-9, HT-9 and HT-7 steels. After exposure in lithium at 500°C for 963, 1295, 1707, 2115 and 2495 hours the weight changes of the corroded specimens were analyzed using a scanning electron microscope and electron probe. The results showed that big differences exist between the auste-nitic stainless steels and the ferritic steels. Besides, the effects of nitrogen content on the lithium corrosion behavior of the alloys are also given.

Effect of sodium cation on lithium corrosion in aprotic media

The present paper discusses the effect of Na + on the characteristics of lithium cells. The lithium cycling efficiency and the capacity retention of cathodically deposited lithium and of Li/MnO 2 and Li/Bi 2O 3 cells are much lower in electrolytes containing Na +. This deterioration in characteristics is accounted for by an enhancement of lithium anode corrosion in the presence of Na + in the electrolyte. The corrosion mechanism is described.

Primary and Secondary Lithium Passivation Characteristics and Effects in the Li / SO 2 Couple

The characteristics and effects of the lithium passivation layer in the lithium sulfur dioxide cell have been studied. Four aspects have been investigated: (i) passivation layer‐induced polarization; (ii) effects of long‐term, low discharge rates; (iii) chemistry of the lithium passivation layer; and (iv) kinetics of the passivation layer growth. Polarization studies showed that an initial polarization (voltage delay) was in some cases followed by a secondary polarization. Studies of the effects of long‐term, low discharge rates indicated that low discharge rates modified the lithium passivation layer, which resulted in increased lithium corrosion and decreased cell capacity. The degradation was greater at higher temperature. Results of studies of the chemistry and formation kinetics of the lithium passivation layer were interpreted in terms of a primary layer, which was responsible for the passivation, and a thicker, porous secondary layer. Formation of the secondary layer is exacerbated by partial discharge. The secondary layer results from precipitation of the Li corrosion products, and was found to contain , , and , where . The primary layer is responsible for the initial polarization (voltage delay) under load, whereas the secondary layer induces a second polarization that inhibits high‐rate discharge.