Surface Film Formation Research Articles

Quantitative Analysis of Solid Electrolyte Interphase and Its Correlation with The Electrochemical Performance of Lithium Ion Batteries Using Concentrated LiPF6/propylene Carbonate

The charge and discharge performance of graphite negative and LiNi0.5Co0.2Mn0.3O2 (NCM523) positive electrodes in highly concentrated 4.45 mol kg−1 LiPF6/propylene carbonate electrolyte solution was investigated to clarify the chemical species in the surface film formed on both electrode surfaces, and compared with those obtained with conventional 1 mol l−1 LiPF6/ethylene carbonate + dimethyl carbonate electrolyte solution. For the graphite negative electrode, the total electrons consumed to form surface film was well correlated with irreversible capacity, and total mole number and chemical species of the surface film were also correlated with interfacial resistance. In the conventional electrolyte solution, the reductive decomposition of solvents progressed preferentially, while LiPF6 decomposed to form surface film in the concentrated electrolyte solution. While both organic- and inorganic-based surface films can achieve high coulombic efficiency and high capacity retention over charge/discharge cycles, the inorganic-based surface film resulted in a significant increase in interfacial resistance. As for the NCM523 positive electrode in the concentrated electrolyte solution, the formation of inorganic-based surface film and a remarkable increase in interfacial resistance were observed clearly, as with the graphite electrode. However, there was no direct correlation among mole number of chemical species in surface films formed, their chemical composition and interfacial resistance.

Anti-Corrosive Behaviour of Saccharum officinarum Extract in 15% HCl for Stainless Steel-410 Surface

The objective of this study is to experimentally evaluate the inhibition properties of Saccharum officinarum extract in a 15% hydrochloric acidic media for stainless steel (SS-410). The gravimetric, UV spectroscopy, FTIR and surface morphological studies carried out using SEM, AFM and XRD revealed that the S. officinarum extract protected the SS 410 steel in 15% hydrochloric acidic medium. Gravimetric analysis revealed maximum 95.92 % inhibition efficiency at 4 g/L inhibitor concentration. The computational studies (quantum chemical calculations) were further utilized to understand the concept of chelation mechanism. The surface film formation and other 3D features of S. officinarum extract film over SS-410 surface was confirmed using AFM studies. Adsorption of S. officinarum extract over SS-410 surface followed Langmuir adsorption isotherm. It is clear from the theoretical and computational studies that the S. officinarum extract acted as mixed type inhibitor by adsorption of hybrid organic-inorganic inhibitor ingredients on SS-410. Thus, S. officinarum extract can develop an efficient protective layer on SS-410 that has various industrial applications.

Influence of physico-chemical parameters of surface-active systems components for minimization of evaporation of hydrocarbon liquids

Highly efficient stable aerated hydrophilic compositions containing fluorotensides and ultralight microdisperse systems using gas-filled glass, aluminosilicate and polymer microspheres have been developed. Designing the compositions of PAS based on the surface activity of surfactants, their solubility in water and the ability to bind water and the formation of hydrogen bonds between the components. The main condition for the stability of the coating when mixing the components - the chemical interaction between them and the formation of a system that does not dissolve in hydrocarbons and does not break down in terms of use. The best film-forming characteristics necessary for the operation of the coating (simultaneous reduction of surface tension and film formation) active substances (FPAR), the non-polar part of the molecules of which contains a fluorocarbon chain, so they are insoluble in hydrocarbons, well soluble in water and easily distributed on the surface of hydrocarbon liquids, creating a protective film. The choice of co-surfactants was based on the ability to stabilize hydrophilic films on the surface of hydrocarbons not only at favorable HLB, but also at the lowest, although higher than the critical concentration of micelle formation (CCM), concentrations for forming a mixed adsorption layer of increased strength. This surfactant was water-oil-soluble twin-80, which will significantly increase the hydrophilic part and enhance the stability of the PAS and the stability of the aerated system. The introduction of glass microspheres into the components of the system has significantly enhanced its strength and stability. In the study of the stability and gas permeability of the developed surfactant systems, it was found that the insulating ability of the coating increases with increasing hydrophilic-lipophilic balance of the system and due to chemical interaction between the carboxyl group of fluorotenside and hydroxyl groups of surfactants.

Al0.3CrxFeCoNi high-entropy alloys with high corrosion resistance and good mechanical properties

The effects of the Cr content on microstructure, corrosion behavior, and mechanical properties of the Al0.3CrxFeCoNi high-entropy alloys (HEAs) were studied. The Al0.3CrxFeCoNi alloys with x = 0–1.0 exhibited the single face-centered-cubic (FCC) structure, and the alloys with x = 1.5–2.0 consisted of the FCC and disordered body-centered-cubic (BCC)/ordered BCC (B2) structure. In the 3.5 mass% NaCl solution, the Al0.3CrxFeCoNi alloys are spontaneously passivated, and the pitting resistance of the alloys was improved with increasing the Cr content in the alloys. It is notable that the Al0.3CrxFeCoNi (x = 1.5–2.0) alloys with Cr-rich FCC and BCC phases demonstrated excellent pitting-corrosion resistance and low corrosion rates of less than 10−3 mm/year due to the formation of the protective surface films enriched in Cr2O3. Moreover, the Al0.3CrxFeCoNi (x = 0–1.0) alloys with the FCC structure exhibited relatively-low tensile strength and large elongation. The further increase in the Cr content to x = 1.5–2.0 improved the strengths and hardness of the alloys due to the increase in BCC/B2 phases. The Al0.3CrxFeCoNi (x = 1.5–2.0) alloys with high corrosion resistance presented good mechanical properties, including tensile strengths of 640–1078 MPa and tensile elongations of 11–44%. It is also demonstrated that increasing the Cr content of Al–Cr–Fe–Co–Ni HEAs is an effective approach for tailoring corrosion-resistant HEAs.

Fourier analysis of an electrochemical phase formation model enables the rationalization of zinc-anode battery dynamics

The efficiency of safe, cheap and sustainable zinc-anode batteries is critically affected by the time-dependent formation of surface films that can impede the utilization of the active material. Knowledge regarding the nature and, in particular, the dynamics of these films is strongly wanting and both theoretical and experimental tools to rationalize the empirically observed behaviour are poorly developed. The present investigation concentrates on the electrode oscillating behaviour and presents an original experimental monitoring approach – based on the joint measurement of electrical and optical quantities - together with its physico-chemical modelling. The mathematical model considered is the DIB model of electrochemical phase formation, in its spatially homogeneous version: that is an ODE system coupling the dynamics of morphology and chemistry. The DIB parameters correspond to specific working conditions of the anode. Firstly, we analyse a Parameter Identification Problem (PIP) based on Fourier regularization. Secondly, a specific PIP is proposed for relaxation oscillations, based on the analysis of the geometry of the limit cycle. The results of this work allow a notable step forward in the understanding on zinc-anode instabilities and open up the perspective of closed-loop control of anode activity state, in view of battery control, also exploiting the higher sensitivity enabled by jointly transducing electrical and optical quantities.

Techno-Economic Assessment: Food Emulsion Waste Management

Production of food-grade emulsions is continuously rising globally, especially in developing countries. The steepest demand growth is in the segment of inexpensive meat products where edible emulsions serve as lubricants to mitigate economic loses linked with mechanical damage during automated processing of artificial casings. Provided that production goal is to minimize emulsion transfer into the product, its vast majority becomes voluminous greasy and sticky waste. Public sewage treatment plants cannot process such waste, its cleaning processes tends to collapse under loads of emulsions. To make matters worse, composition of emulsions often changes (according to actual pricing of main components) and emulsion manufacturers carefully guard their recipes. Therefore, running of in-house sewage plants would require continuous experimentation linked with need for skilled personnel, frequent changes in technology setup and high operating costs in general. Consequently, it was repeatedly and independently reported that emulsion waste is poured onto wildlife, resulting in environmental damage and an intense rotting odor. Three new methods of emulsion breakdown are proposed and techno-economically assessed. High versatility of methods was confirmed and multiple austerity measures were incorporated. Emulsions are also assessed in terms of an energy source for aerobic and anaerobic microorganisms. It is reported that the addition of edible emulsion to compost does not result in increased product quality or cost reduction. It is firstly revealed that edible emulsions can instantly create an anaerobic environment and accelerate biogas production through the formation of surface films on feedstock surface. Adding waste food-grade emulsions to the biogas plant makes it possible to 100% reduce process water consumption in biogas stations as the process speed can be shortened by approximately 12%.

Accelerated Formation of Surface Films on the Degradation of LiCoO 2 Cathode at High Temperature

Accelerated Formation of Surface Films on the Degradation of LiCoO 2 Cathode at High Temperature

Toward a Physical Description of the Role of Germanium in Moderating Cathodic Activation of Magnesium

The role played by surface film formation in moderating cathodic activation (i.e., H2 evolution associated with anodic dissolution in NaCl [aq]) was determined for an Mg-0.3Ge (wt%) alloy and contrasted with this process in pure Mg. Cathodic activation was not detected using the scanning vibrating electrode technique (SVET) during anodic dissolution of the Mg-0.3Ge alloy under either freely corroding or anodic polarization conditions. Filament tracks that initiated under the more aggressive testing condition remained electrochemically inert. However, volumetric H2 evolution measurements revealed that Ge alloying additions “switch off” the remote cathodes observed on previously corroded pure Mg surfaces, while Ge additions did not eliminate the “local” cathode at the principal sites of anodic activity (which cannot be detected by SVET). As such, the quantity of H2 measured on the corroding Mg-0.3Ge alloy arises exclusively from cathodic H2 evolution at the anodic sites. Moderation of sustained cathodic activation by alloying with Ge was associated with the incorporation of Ge into the inner MgO/Mg(OH)2 layer during anodic dissolution of Mg. It is possible that entrapped Ge particles or GeO2 serve as an effective poison for H recombination in the overall H2 evolution reaction that would otherwise readily occur on freshly formed Mg(OH)2 at anodic dissolution sites.

Phase-Species-Dependent Electrochemical and Corrosion Behaviors of Wrought Mg-Y-Zn-Based Alloys

The electrochemical and corrosion behaviors of the wrought Mg-Y-Zn-based alloys with different phase species have been systematically investigated to compare the role of phase species in the corrosion performance. The X-Mg12YZn phase contributes a superior corrosion inhibiting effect over the W-Mg3Y2Zn3 phase. The corrosion rate of Mg-Y-Zn alloy bearing X-Mg12YZn phase is 13.09 mm year−1, which is lower than that of the alloy bearing W-Mg3Y2Zn3 phase (16.67 mm year−1). This is because the X-Mg12YZn platelike phase plates are more effective and durable than W-phase particles to release Y element during surface film formation. The small W-Mg3Y2Zn3 phase particles may drop out from the corrosion scale, resulting in the mass loss and breakdown of the protective surface film during the propagation of corrosion into inner layers. The related corrosion mechanism has been discussed in detail.

Understanding the Surface Film Formation on Si Electrodes in Lithium Secondary Batteries with Atomic Force Microscopy.

The solid electrolyte interphase formation on the negative electrodes of lithium secondary batteries has been considered as one of the principal issues limiting the performance of batteries. Si is an attractive electrode material for improving energy density of lithium secondary batteries because of its high specific theoretical capacity (4200 mAh g-1). However, solid electrolyte interphase formation on Si-based electrodes have not been clearly understood in spite of its significance. Herein, the solid electrolyte interphase formation on Si electrodes in electrolyte solutions containing ethylene carbonate or propylene carbonate was investigated by using in-situ atomic force microscopy. Large and irreversible capacity fade in SiO electrodes was confirmed in both electrolyte solutions through cyclic voltammetry and charge/discharge testing. The in-situ atomic force microscopy results indicated that the decomposition reaction occurred in the ethylene carbonate-based electrolyte solution at a potential of ~0.68 V, while the lithium alloying reaction occurred below 0.25 V during the first reduction process. The decomposition reaction was more vigorous and occurred at a higher potential in the propylene carbonate-based electrolyte solution, resulting in the formation of a thick solid electrolyte interphase film. These results suggest that the solid electrolyte interphase formation on Si electrodes is strongly influenced by the composition of the electrolyte solution.

Targeted research on the single role of lithium Bis(oxalate)borate in the film-forming process through a novel lithium salt-free electrolyte system

A blank comparison group of lithium salt-free electrolyte system, replacing the lithium salt of electrolyte with a redox shuttle agent, is constructed to give targeted research on the single role of lithium bis(oxalate)borate (LiBOB) salt, especially of bis(oxalate)borate anions (BOB−) in the film-forming process. By combining and comparing all available studies, such as attenuated total reflectance (IR-ATR), X-Ray photoelectron diffraction spectrum (XPS), electrochemical impedance spectrum (EIS), scanning electron microscopy (SEM) tests and quantum chemical calculation, the formation mechanism of the solid electrolyte interphase (SEI) film is proposed. Results reveal that the prior reduction of BOB− anions can postpone the reduction potential and hinder the decomposition rate of carbonate solvents, but promote the formation of a dense, conductive and effective SEI film. This work provides a novel way to investigate the film-forming mechanism and has guiding significance for revealing the effect of other kinds of lithium salts on the surface film formation.

Anti-cognition in lithium-ion battery electrolytes: Comparable performance with degraded electrolyte

The stability of electrolytes is extremely important for the lithium-ion battery industry. However, research on electrolyte stability is lacking. Many film-forming additives are investigated to improve the interface stability of the cathode and electrolyte. However, many additives are unstable even in ambient environments, which results in additional costs in electrolyte cryogenic transportation and storage. Herein, we conduct in-depth research on the performance of high-voltage batteries influenced by the stability additives containing electrolytes. The capacity retention is only 44% and 20% after 150 cycles using standard (STD) electrolyte in LiNi0.5Mn1.5O4/Li and xLi2MnO3·(1-x) LiMO2/Li batteries, respectively. Film-forming additives usually promote the cycling performance of batteries. Surprisingly, after storage for 30 days, the batteries with yellowing electrolyte show better cycling performances. The LiNi0.5Mn1.5O4/Li and xLi2MnO3·(1-x) LiMO2/Li batteries achieve 92% and 75% capacity retention with a coulombic efficiency of 99.2% and 99.1% after 150 cycles, respectively, which performs better than fresh electrolyte. Following measurements indicate that the additive decomposition product can contribute to the formation of surface films, which inhibits continuous decomposition of the electrolyte and impedes pulverization of the cathode electrode. This work counters current conceptions of degraded electrolyte and is informative for the industrial applications of unstable additive-containing electrolytes.

A Novel Multi-Functional Electrolyte Additive for Ni-Rich Cathode Materials

Ni-rich layer oxides Li[Ni x CoyMn1−x−y ]O2 (x ≥ 0.8, NCMs) are promising advanced cathode materials for high-energy Li-ion batteries because of their high specific capacity (≥ 200 mAh g−1) with an average discharge voltage of 3.8 V vs Li+/Li, as compared to the commercialized cathode materials (e.g. LiCoO2, LiFePO4).1 However, the instability of cathode–electrolyte interface causes the structural degradation of cathode active material and the electrolyte consumption, as well as gas evolution due to oxidative decomposition of electrolyte, resulting in a rapid capacity fading.2 Thus, improvement in the stability of cathode–electrolyte interphase is a key requirement to inhibit their structural degradation and enhance their electrochemical properties. The formation of a protective surface film via electrolyte additives is considered a cost-effective and reliable way to improve the cathode–electrolyte interfacial stability, as the stable surface film, uniformly distributed over the entire cathode surface, would prevent direct contact of oxide with the electrolyte, still allowing Li+ transport between the cathode and electrolyte.3 In this work, we report the high-performance NCM cathode through interfacial stabilization using a novel electrolyte additive. The details of surface film stability and formation mechanism, and their relation to gas evolution as well as cycling performance would be discussed.

Anodic Dissolution of Copper in the Aluminum Chloride-1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

The ever popular AlCl3-1-ethyl-3-ethylimidazolium chloride (EtMeImCl) ionic liquid (IL) system offers a unique solvation environment for many metal ions. In fact, the use of these chloroaluminate ionic liquids for the electrochemical surface finishing of metals was recently reviewed.1 These ionic liquids display adjustable Lewis acidity that depends directly on the mole ratio of the AlCl3 to the organic salt. The basic AlCl3-EtMeImCl mixture, which contains coordinately unsaturated Cl-, provides a solvation environment similar to aqueous HCl and NaCl, except of course without the complications due to the H2O solvent or H3O+. The opposite situation prevails in the Lewis acidic ionic liquid because the main chemically active ionic component of the ionic liquid is the coordinately unsaturated species, [Al2Cl7]-. Thus, there are no “hard” ligands available to form stable, isolable anionic complexes with the anodization product. Recently, both composition regions of the AlCl3-EtMeImCl IL system have been explored for the electrodissolution/electropolishing of Al.2 The advantages afforded by anodic dissolution of metals in this ionic liquid relative the aqueous acids and salt solutions commonly used for this purpose are quite obvious, i.e., the avoidance of the oxide surface films that invariably complicate the metal electropolishing process. In this paper, we report the thermodynamics and kinetics of the anodic dissolution of copper metal in the acidic and basic compositions of the AlCl3-EtMeImCl ionic liquid. In the former, the dissolution of copper at a Cu-RDE exhibits mixed control. No limiting current or passivation due to the formation of an insoluble surface film was apparent. In the basic composition region, mixed control was observed at small overpotentials, but as the overpotential was increased, a limiting current was obtained that scaled linearly with the Cl- concentration in the ionic liquid. The connection between these results and the mechanism of the dissolution process will be discussed.____________________________________________ 1. T. Tsuda, G. R. Stafford and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017).2. C. Wang and C. L. Hussey, J. Electrochem. Soc., 163, H1186 (2015).

Kinetics of Induced Deposition of Films Based on Tetrakis(4-Aminophenyl)Porphyrin

This work confirms formation of surface films of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (H2T(4-NH2Ph)P) in dimethylsulfoxide in the potential range of oxygen electroreduction. Kinetics of variation of faradaic currents and of the interface characteristics are studied at the working electrode potentials of +0.5 V (porphyrin electrooxidation), –0.9 V (oxygen electroreduction), and –1.25 V (coreduction of porphyrin and oxygen). It is shown that the working electrode surface is passivated at the potential of +0.5 V and faradaic currents decrease fast. At the potentials of –0.9 and –1.25 V, the working electrode surface passivation is less pronounced. As shown by analysis of electrode impedance spectra, a film is formed on the electrode surface under electroreduction conditions (–0.9 and –1.25 V), as opposed to electrooxidation conditions (+0.5 V). Charge transport through this film can be characterized by modeling the interface impedance. The kinetics of variation of the interface parameters allow estimating the stage mechanism of film formation and restructuring of the formed layer.

Improved Performance of Li-metal∣LiNi0.8Co0.1Mn0.1O2 Cells with High-Loading Cathodes and Small Amounts of Electrolyte Solutions Containing Fluorinated Carbonates at 30 °C–55 °C

Herein, we report on the performance of stable lithium metal ∣ LiNi0.8Co0.1Mn0.1O2 (NCM 811) cells with practical electrodes loading of 3.4 mAh cm−2 and small amounts of electrolyte solutions, at 30 °–55 °C. The latter contained 1 M LiPF6 in fluoroethylene carbonate (FEC)/difluoroethylene carbonates (DFEC)/dimethyl carbonate (DMC) 1:1:8, around 0.7–1.7 μl mg−1 of active cathode material (14–33 μl cm−2). Using DFEC as a co-solvent enables to overcome drastic capacity fading of Li metal∣NCM cells containing practical amounts (≤1.2 μl mg−1NCM 811) of electrolyte solutions based on FEC/DMC. The lithium metal anodes were characterized by scanning electron microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). The surface films formed on Li anodes cycled in solutions containing FEC and DFEC are composed mainly of their reduction products. In solutions containing FEC and DFEC the role of the latter is to prevent a fast consumption of FEC, by the formation of surface films enriched with its reduction products. Then, minor FEC surface reactions maintain effective electrodes passivation during prolonged cycling. This work clarifies the important role of fluorinated alkyl carbonate co-solvents in stabilizing high energy density secondary batteries based on Li metal anodes.

Cathode Interfaces: Effect of Electrolyte Additives on the LiNi0.5Mn0.3Co0.2O2 Surface Film Formation with Lithium and Graphite Negative Electrodes (Adv. Mater. Interfaces 1/2020)

Cathode Interfaces: Effect of Electrolyte Additives on the LiNi_0.5Mn_0.3Co_0.2O₂ Surface Film Formation with Lithium and Graphite Negative Electrodes (Adv. Mater. Interfaces 1/2020)

A Stable Solid Electrolyte Interphase for Magnesium Metal Anode Evolved from a Bulky Anion Lithium Salt.

Rechargeable magnesium (Mg) metal batteries are a promising candidate for "post-Li-ion batteries" due to their high capacity, high abundance, and most importantly, highly reversible and dendrite-free Mg metal anode. However, the formation of passivating surface film rather than Mg2+ -conducting solid electrolyte interphase (SEI) on Mg anode surface has always restricted the development of rechargeable Mg batteries. A stable SEI is constructed on the surface of Mg metal anode by the partial decomposition of a pristine Li electrolyte in the electrochemical process. This Li electrolyte is easily prepared by dissolving lithium tetrakis(hexafluoroisopropyloxy)borate (Li[B(hfip)4 ]) in dimethoxyethane. It is noteworthy that Mg2+ can be directly introduced into this Li electrolyte during the initial electrochemical cycles for in situ forming a hybrid Mg2+ /Li+ electrolyte, and then the cycled electrolyte can conduct Mg-ion smoothly. The existence of this as-formed SEI blocks the further parasitic reaction of Mg metal anode with electrolyte and enables this electrolyte enduring long-term electrochemical cycles stably. This approach of constructing superior SEI on Mg anode surface and exploiting novel Mg electrolyte provides a new avenue for practical application of high-performance rechargeable Mg batteries.

Phase transition regulation and Cd-O/Cd-F compounds multi-effect modification synergistically act on LiNi0.5Mn1.5O4 cathode

LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material for lithium-ion batteries due to its high discharge voltage, low cost, environmental friendliness, and high energy density. To enhance the electrochemical performance of LNMO, Cd is innovatively employed as a modifying agent. Structural and morphological characterizations confirm that CdO is successfully wrapped on the surface of LNMO. Further physical, chemical, and electrochemical detections verify the phase transition of LNMO. The CdO-coated samples show excellent cyclability and rate performance. The CdO-coated LNMO (Cd 0.4 wt.%) exhibits a discharge capacity of 133.3 mAh g−1 with a retention rate of 95.2% after 300 cycles at 1-C rate (3.5–4.8 V), while that of the pristine is only 89.4%. Even at 10-C rates, the CdO-coated LNMO has an initial discharge capacity of 120.0 mAh g−1 with a retention rate of 92.3% after 300 cycles at the same voltage limit. Specifically, at the first of cycling, the newly formed Cd-F compounds and CdO layer could suppress the side reactions and reduce the formation of surface film. Finally, the process of kinetics is improved.

Probing the in-depth distribution of organic/inorganic molecular species within the SEI of LTO/NMC and LTO/LMO batteries: A complementary ToF-SIMS and XPS study

Spinel Li4Ti5O12 (LTO) is an attractive candidate for negative electrode materials of Li-ion batteries because of its outstanding safety characteristics. In this paper, the influence of common high voltage cathodes, LiNi3/5Co1/5Mn1/5O2 (NMC) and LiMn2O4 (LMO), upon the electrochemical performances of LTO/LMO and LTO/NMC cells, in relation with the Solid Electrolyte Interphase (SEI) properties formed over the LTO surface, is studied. After cycling, the electrodes were analyzed by ToF-SIMS and XPS with two X-ray sources (Ag and Al) to investigate both the chemical composition and the in-depth distribution of specific SEI species at the electrode surface. Facing both counter-electrodes, LTO electrodes are covered by surface layers due to the degradation of electrolyte components inducing an irreversible capacity loss, more important for LTO/LMO cells. The chemical composition of both layers is similar: organic and inorganic species but the SEI formed on LTO electrode cycled facing LMO electrode is thicker and contains small amounts of manganese compounds from the positive electrode. Moreover, 3D mappings reconstructed from ToF-SIMS depth-profile experiments, display different in-depth spatial distributions of SEI species, which are in agreement with XPS results. Consequently, the impact of interactions between electrodes on the formation of surface films is discussed.