Solvent Decomposition Research Articles

Amphilic Water-Lean Carbon Capture Solvent Wetting Behavior through Decomposition by Stainless-Steel Interfaces.

A combined experimental and theoretical study has been carried out on the wetting and reactivity of water-lean carbon capture solvents on the surface of common column packing materials. Paradoxically, these solvents are found to be equally able to wet hydrophobic and hydrophilic surfaces. The solvents are amphiphilic and can adapt to any interfacial environment, owing to their inherent heterogeneous (nonionic/ionic) molecular structure. Ab initio molecular dynamics indicates that these structures enable the formation of a strong adlayer on the surface of hydrophilic surfaces like oxidized steel which promotes solvent decomposition akin to hydrolysis from surface oxides and hydroxides. This decomposition passivates the surface, making it effectively hydrophobic, and the decomposed solvent promotes leaching of the iron into the bulk fluid. This study links the wetting behavior to the observed corrosion of the steels by decomposition of solvent at steel interfaces. The overall affect is strongly dependent on the chemical composition of the solvent in that amines are stable, whereas imines and alcohols are not. Moreover, plastic packing shows little to no solvent degradation, but an equal degree of wetting.

Impact of Solvent Decomposition on Dispersion Structure of PEFC Catalyst Ink

To achieve higher current density operation of polymer electrolyte fuel cells (PEFCs), it is required to realize higher performance catalyst layer with low oxygen transport resistance, high proton conductivity, and low Platinum loading. Because dispersion structure of catalyst ink strongly affects the catalyst layer structure, it is crucial to understand the dispersion mechanism of PEFC catalyst ink. Uemura et al. reported that the decomposition of ethanol within the catalyst ink strongly affect its dispersion [1, 2], but its mechanism was not fully understood yet. In this study, impact of solvent decomposition on the dispersion of the catalyst ink was investigated.The catalyst inks were fabricated by mixing platinum-supported carbon (TEC10V30E, Tanaka Kikinzoku Kogyo), ionomer (DE1021, Sigma-Aldrich), and water/ethanol solvent. The water/ethanol ratio, the ionomer/carbon ratio and the solid content of the catalyst ink were kept 46wt%, 0.75 and 10%, respectively. To investigate the impact of solvent decomposition, decomposition products of ethanol (aldehyde, acetic acid, and ethyl acetate) were artificially added to the catalyst ink, and its effect on dispersion were evaluated. Viscosity characteristics were measured at each shear rate in the range of 0.01 to 1000 1/s by a rotary rheometer (MCR302, Anton-Paar), and particle size distribution of the undiluted catalyst ink was measured by the laser diffraction type particle size distribution meter (LA-960V2, HORIBA). In addition, ionomer adsorption rate on the platinum-supported carbon was measured by centrifugal separation technique.Figure (a) showed the impact of adding ethanol decomposition on viscosity characteristics. The result showed that aldehyde and ethyl acetate affect the dispersion of the catalyst ink, and it was suggested that generation of aldehyde caused aggregation of the platinum-supported carbon within the ethanol-rich catalyst ink. Figure (b) showed the effect of aldehyde on ionomer adsorption ratio as a function of centrifuge time. By adding the aldehyde, the ionomer adsorption rate became lower. Because the ionomer promotes the dispersion of ionomer, low ionomer adsorption rate might cause the aggregation of platinum supported carbon, and further understanding on the dispersion mechanism is highly requested to realize stable catalyst ink.[1] Suguru Uemura et al 2019 J. Electrochem. Soc. 166 F89[2] Kaname Iida et al 2020 ECS Trans. 98 497 Figure 1

Salting out and vortex-assisted dispersive liquid–liquid microextraction based on solidification of floating organic drop microextraction (SO-VADLLME-SFODME) for extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in water and solid samples followed by HPLC

In this research the possibility of application of an innovative, simple, economical, selective ability and green (environmentally friendly) method of salting out and Vortex-Assisted dispersive liquid-liquid microextraction based on solidification of floating organic drop by using high performance liquid chromatography with containing UV for pre-concentration, the extraction and determination of polysiclic in water and solid samples followed by HPLC was studied. In this method three integrated and combined approaches have been adopted so as to maximize the advantages of the approach used while minimizing their disadvantages. The effects of experimental variables such as pH, the type and volume of dispersive extracting solvents (μl, pH), the volume of organic drop microextraction (extracting solvent), salt density (concentration), centrifuge condition (time), extraction time and temperature were examined, and the process of optimization was obtained by using a software based on Response Surface Methodology (RSM) and Box-Behnken design [as the experimental model] and Desirability Function (DF). This method has appropriate linear calibration between 0.2 to 800μg/L, and a significant limit of detection coefficient (r2> 9991) and low detection range (between 0.05 to 0.09 μg/L). The above method was also applied for the successful determination of polycyclic aromatic hydrocarbons in industrial was water, water and soil samples PAHs) and the percentage of recycling, repeatability and reproducibility, resulting in satisfactory results. Simplicity, being economical, quickness, proper repeatability, less consumption of organic solvent and efficient decomposition are of the principal advantages (merits) of the proposed method for the decomposition and determination of polycyclic aromatic hydrocarbons (PAHs) in water samples.

Impact of Solvent Decomposition on Dispersion Structure of PEFC Catalyst Ink

To achieve high current density operation of polymer electrolyte fuel cells (PEFCs), high performance catalyst layer is requested. Though dispersion structure of catalyst ink strongly affects the catalyst layer structure, dispersion mechanism of the catalyst ink has not been understood. In this study, to understand the impact of solvent decomposition on the dispersion of the catalyst ink, the decomposition products of the ethanol were artificially added to the catalyst ink, and the impacts of each decomposition products on rheology characteristics and ionomer adsorption rate on platinum supported carbon (Pt/C) of the catalyst inks were investigated. The results showed that the aldehyde lower the ionomer adsorption rate and increased viscosity. Because the ionomer works as surfactant within the catalyst ink, lower ionomer adsorption rate might cause aggregation of the Pt/C, and further understanding about impacts of decomposition products are highly requested to control the dispersion structure of the catalyst ink.

Near-Infrared Femtosecond Laser Ablation of Au-Coated Ni: Effect of Organic Fluids and Water on Crater Morphology, Ablation Efficiency and Hydrodynamic Properties of NiAu Nanoparticles.

Scanning electron microscopy (SEM) and profilometry of the crater morphology and ablation efficiency upon femtosecond laser ablation of Au-coated Ni targets in various fluids revealed a pronounced dependence on the ablation medium. For ethanol, a sufficient ablation efficiency was obtained, whereas for 2-butanol a higher efficiency indicated stronger laser–target interaction. Hierarchical features in the crater periphery pointed to asymmetrical energy deposition or a residual effect of the Coulomb-explosion-initiating ablation. Significant beam deviation in 2-butanol caused maximum multiple scattering at the crater bottom. The highest values of microstrain and increased grain size, obtained from Williamson–Hall plots, indicated the superposition of mechanical stress, defect formation and propagation of fatigue cracks in the crater circumference. For n-hexane, deposition of frozen droplets in the outer crater region suggested a femtosecond-laser-induced phase explosion. A maximum ablation depth occurred in water, likely due to its high cooling efficiency. Grazing incidence micro X-ray diffraction (GIXRD) of the used target showed residual carbon and partial surface oxidation. The produced nanoparticle colloids were examined by multiangle dynamic light scattering (DLS), employing larger scattering angles for higher sensitivity toward smaller nanoparticles. The smallest nanoparticles were obtained in 2-butanol and ethanol. In n-hexane, floating carbon flakes originated from femtosecond-laser-induced solvent decomposition.

1,4-Dicyanobenzene as electrolyte additive for improve electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode materials in lithium metal rechargeable batteries

The cycling stability of Li1.2Ni0.2Mn0.6O2 cathodes is increased enormously by adding 0.1 %wt 1,4-dicyanobenzene (1,4-DCB) additive in the electrolyte, and the capacity retention increases from 20.3% to 63.8% after 350 cycles. It is found that 1,4-DCB eliminates the trace water in the electrolyte via hydrolysis under acidic conditions. A coating layer on the electrode surface is formed by preferentially oxidized of 1,4-DCB, which reduce the contact between electrolyte and cathode, inhibiting the decomposition of electrolyte solvent. N group in the electrooxidation product of 1,4-DCB can combine with PF5 to improve the stability of LiPF6, then reducing the decomposition of LiPF6. The benzene ring and conjugated bond of 1,4-DCB are favorable for the transfer of interfacial electron and ion, and then the electrochemical performance of lithium-rich layered materials is improved.

Lithium anode in carbonate-based electrolyte: High-performance by self-protected solid-electrolyte-interphase

Lithium metal is considered as the ultimate negative electrode for future high-energy batteries because of its lowest electrode potential and very high theoretical capacity. However, its practical application is severely plagued by the hazardous lithium dendritic growth upon charge and low coulombic efficiency resulting from the inhomogeneous mass and charge transfers across the Li/electrolyte interface. Herein we report an economical and effective approach to step out of this dilemma, using self-protected Solid electrolyte interphase (SEI) in carbonate-based electrolyte with Vinylethylene carbonate (VEC) additive. VEC as a sacrificing material can prevent the Li salts and solvent decomposition, and further free radical reaction of VEC decomposition products in-situ form self-protected highly uniform and mechanical strength SEI layer on Li metal surface. The versatile effects of this unique SEI layer are demonstrated by the uniform lithium plating/stripping and very high Coulombic efficiency (up to 96% after 150 cycles at 1 mA cm−2 with 1 mAh cm−2). Lithium metal batteries, employing the self-protected Li metal negative electrode coupled with LiFePO4, exhibit excellent performance in both cycling stability and rate capability. Even the anode free cell Cu|NMC811, an impressive high initial coulombic efficiency of 92.5% and promising improvement of cycling performance are achieved.

Fundamental Flaw in the Current Construction of the TiO2 Electron Transport Layer of Perovskite Solar Cells and Its Elimination

The top-performing perovskite solar cells (efficiency > 20%) generally rely on the use of a nanocrystal TiO2 electron transport layer (ETL). However, the efficacies and stability of the current stereotypically prepared TiO2 ETLs employing commercially available TiO2 nanocrystal paste are far from their maximum values. As revealed herein, the long-hidden reason for this discrepancy is that acidic protons (∼0.11 wt %) always remain in TiO2 ETLs after high-temperature sintering due to the decomposition of the organic proton solvent (mostly alcohol). These protons readily lead to the formation of Ti-H species upon light irradiation, which act to block the electron transfer at the perovskite/TiO2 interface. Affront this challenge, we introduced a simple deprotonation protocol by adding a small amount of strong proton acceptors (sodium ethoxide or NaOH) into the common TiO2 nanocrystal paste precursor and replicated the high-temperature sintering process, which wiped out nearly all protons in TiO2 ETLs during the sintering process. The use of deprotonated TiO2 ETLs not only promotes the PCE of both MAPbI3-based and FA0.85MA0.15PbI2.55Br0.45-based devices over 20% but also significantly improves the long-term photostability of the target devices upon 1000 h of continuous operation.

Combination of cold induced HLLME with an effervescence-assisted DLLME based on deep eutectic solvent decomposition; application in extraction of some pyrethroid and carbamate pesticides from edible oils

ABSTRACT A cold-induced homogenous liquid–liquid microextraction method combined with solidification of floating organic droplets effervescent-assisted dispersive liquid–liquid microextraction has been developed for simultaneous extraction of several pyrethroid and carbamate pesticides from edible oils. The extracted analytes were determined by high performance liquid chromatography-diode array detector. For this purpose, 5 mL of edible oil sample was transferred into a glass test tube and it was mixed with 150 µL α-terpineol: acetic acid deep eutectic solvent. After vortexing (for 5 min), the mixture was placed into an ice: sodium chloride bath to adjust the solution temperature at −16℃. In this step, the oil sample was solidified, and the deep eutectic solvent was collected on top of the oil. Thus, it was collected and dispersed into 5.0 mL sodium carbonate solution at a concentration of 1.0 mol/L containing 2.5% w/v sodium chloride. In this step, the deep eutectic solvent was decomposed in the solution and α-terpineol dispersed in the sample solution. To obtain high extraction efficiency the effective parameters were optimised and under optimal conditions, the method showed broad linear ranges (2.6–500 ng/mL) with good coefficient of determinations ≥0.994. The extraction recoveries and enrichment factors of the method were in the ranges of 78–93% and 98–116%, respectively. The limits of detection and quantification were within the range of 0.2–0.8 and 0.6–2.6 ng/mL, respectively. The method was successfully used for the determination of the analytes in different edible oil samples.

Improved Low Temperature Performance of Graphite/Li Cells Using Isoxazole as a Novel Cosolvent in Electrolytes

An investigation of novel electrolyte formulations to improve low temperature performance of Li/graphite half cells has been conducted. A novel electrolyte co-solvent, isoxazole (IZ), has been investigated in electrolyte systems composed of lithium difluoro(oxalato)borate (LiDFOB) in fluoroethylene carbonate (FEC) and LiDFOB in ethylene carbonate (EC). Cells containing 1 M LiDFOB FEC: IZ electrolyte have a significant improvement in capacity retention and reversible capacity at −10 °C. Ex-situ surface analysis of the cycled electrodes suggests that reduction of LiDFOB results in an oxalate rich solid electrolyte interphase (SEI). Addition of FEC, results in improved stability of the anode SEI preventing further decomposition of isoxazole solvent and improving cycling performance.

Enhanced Cycling of Ni-Rich Positive Electrodes by Fluorine Modification

Ni-rich positive electrodes for Li-ion batteries can provide enhanced initial discharge capacity yet suffer from significant capacity degradation upon cycling. Fluorination of Ni-rich NMC811 positive electrodes results in a capacity retention of more than 90% after 100 cycles upon cycling to 4.4 VLi. The increased cycling stability of F-modified NMC811 can be attributed to the modification of the oxide electronic structures, where density functional theory calculations shows that incorporating fluorine into the oxide lattice decrease the driving force of carbonate dissociation on the oxide surface. In situ infrared (IR) spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS) further supports this argument by showing less carbonate oxidation for F-modified LiNi0.8Mn0.1Co0.1O2 (NMC811) than as-received NMC811 upon charging. The reduced carbonate oxidation is coupled with minimal salt decomposition on the electrode surface, as revealed by XPS. Further comparing in situ IR and XPS with that of the heat-treated NMC811 and Li2CO3 allows for decoupling the solvent decomposition products, where oxides are responsible for the vinylene carbonate formation with two hydrogens removed whereas surface metal carbonates promote dehydrogenated ethylene carbonate with just one hydrogen removed. This work points towards the importance of the anion engineering to increase the cycling stability of Ni-rich NMC positive electrodes.

Ultrasound-assisted liquid–liquid microextraction based on solidification of floating organic droplet using deep eutectic solvent as disperser for preconcentration of Ni and Co

ABSTRACT An ultrasonic-assisted demulsified dispersive liquid–liquid microextraction based on solidification of floating organic droplet (UA-DE-DLLME-SFO) technique was considered for the preconcentration of Co and Ni before their determination by micro sampling flame atomic absorption spectrometry (FAAS). In this method, the sample solution was mixed with 1-dodecanol as an extractant and a deep eutectic solvent (tetrabutylammonium bromide: acetic acid) as a dispersive solvent. The dispersion of extraction solvent was performed through the decomposition of deep eutectic solvent in the sample solution. Ultrasonication promoted the dispersion of the extraction solvent into the sample solution. After dispersing, acetonitrile as a demulsifier was introduced to break down the emulsion quickly without centrifugation. The influence of the experimental variables on the extraction recoveries was optimised. The limits of detection were found to be 0.2 µg L−1 and 0.4 µg L−1 with the preconcentration factors of100 for Co and Ni, respectively. The relative standard deviations (RSDs, %) (50 µg L−1, n = 10) were 2.5% and 3.4%, for Co and Ni, respectively. The accuracy of the method was checked through the analysis of certified reference materials namely NIST SRM 1643bof water sample, SRM 1568aof rice flour, and FAPAS QC material of brown rice (T07370 QC). The recoveries of Co and Ni added in water and food samples were obtained in the range of 92.6–98.5% and 92.9–101.5% respectively.

Solvent and catalyst-free synthesis of In2O3 octahedron using single-step thermal decomposition technique for NO2 detection

In this article, a highly crystalline In2O3 octahedron has been synthesized by a single-step solvent and catalyst-free thermal decomposition method. The as-synthesized sample has been characterized using XRD, FESEM, HR-TEM, and XPS. The characterization results confirmed the formation of the cubic phase of the In2O3 sample with the octahedron morphology. The gas sensing characteristics of the In2O3 octahedron sample for oxidizing and reducing gases have been investigated systematically. The optimum operating conditions for selective detection of chemical inputs have been determined. Additionally, a maximum sensor response (~4252%) along with fast response (recovery) times ~30 s (13 s) has been obtained for NO2 gas (30 ppm) at its operating temperature 200 °C. The results suggested that the In2O3 octahedron sensor proposes a promising candidate for NO2 detection at its optimum operating temperature of 200 °C and can open up new ways to integrate these sensors with future electronic devices.

Sulfur is a New High-Performance Additive toward High-Voltage LiNi0.5Co0.2Mn0.3O2 Cathode: Tiny Amount, Huge Impact.

Increasing working voltage of cathode has been identified as one of the most promising strategies to increase energy density of the lithium-ion batteries. It is of crucial importance to suppress side reactions and control the formation of a cathode electrolyte interface (CEI) on the cathode surface in a high voltage range. In this work, sulfur is utilized to increase the working voltage of LiNi0.5Co0.2Mn0.3O2(NCM 523) to 4.5 V as demonstrated by both the NCM523/Li half-cell and NCM 523/graphite full cell. When a tiny amount of sulfur (0.1 mg mL-1) is added to the blank electrolyte of ethylene carbonate (EC) and dimethyl carbonate (DMC) (3:7 by volume), the cycling stability and rate performance are greatly improved in the NCM523/Li half-cell. The capacity retention over 200 cycles at 170 mA g-1 (1.0 C) is increased from 61.2 to 82.0%. The capacity at a high current density of 850 mA g-1 (5.0 C) is increased from 92 mAh g-1 to 120 mAh g-1. Because the addition of sulfur also enhances the performance of the Li/graphite half-cell, improved performance is demonstrated by the NCM 523/graphite full cell as well. The mechanism is interpreted based on various characterizations. It is revealed that the preferential oxidation of sulfur at the cathode surface suppress decomposition of electrolyte solvent. Because only a tiny amount of sulfur is added into the electrolyte solution, excessive decomposition of sulfur is avoided, leading to improved electrochemical performance.

Elucidating and Tuning Catalytic Sites on Zirconium- and Aluminum-Containing Nodes of Stable Metal–Organic Frameworks

ConspectusMetal-organic frameworks (MOFs) are a huge, rapidly growing class of crystalline, porous materials that consist of inorganic nodes linked by organic struts. Offering the advantages of thermal stability combined with high densities of accessible reactive sites, some MOFs are good candidate materials for applications in catalysis and separations. Such MOFs include those with nodes that are metal oxide clusters (e.g., Zr6O8, Hf6O8, and Zr12O22) and long rods (e.g., [Al(OH)]n). These nanostructured metal oxides are often compared with bulk metal oxides, but they are in essence different because their structures are not the same and because the MOFs have a high degree of uniformity, offering the prospect of a deep understanding of reactivity that is barely attainable for most bulk metal oxides because of their surface heterogeneity. This prospect is being realized as it has become evident that adventitious components on MOF node surfaces, besides the linkers, are crucial. These ligands arise from modulators, solvents, or products of solvent decomposition in MOF synthesis solutions, and because they are minor components that are often irregularly placed on defects, they may not show up in X-ray diffraction (XRD) crystal structures. Hydroxyl groups on the nodes (like those on bulk metal oxides) are regarded as native functional groups arising from solvent water, but they may barely be present initially, with common ligands instead being formate and acetate formed from modulators formic acid and acetic acid. (Formate also arises from the decomposition of dimethylformamide (DMF) solvent.) Replacement and control of the node ligands is facilitated by postsynthesis reactions (e.g., with alcohols or aqueous HCl/H2SO4 solutions) or as a result of high-temperature decomposition. In catalysis, adventitious node ligands can be (a) reaction inhibitors that block active sites on the nodes (e.g., formate blocking Zr, Hf, or Al Lewis acid sites); (b) reaction intermediates (e.g., ethoxy in ethanol dehydration); or (c) active sites themselves (e.g., terminal OH groups in tert-butyl alcohol (TBA) dehydration). Surprisingly, in view of the catalytic importance of such ligands on bulk metal oxides, their subtle chemistry on MOF nodes is only recently being determined. We describe (1) methods for identifying and quantifying node ligands (especially by IR spectroscopy and by 1H NMR spectroscopy of MOFs digested in NaOH/D2O solutions); (2) node ligand surface chemistry expressed as reaction networks; (3) catalysis, with mechanisms and energetics determined by density functional theory (DFT) and spectroscopy; and (4) MOF unzipping by reactions of linker carboxylate ligands with reactants such as alcohols that break node-linker bonds, a cause of catalyst deactivation and also an indicator of node-linker bond strength and MOF stability.

Mechanistic Study of the Effect of Epoxy Groups on Ethylene Carbonate Decomposition Reaction on Carbon Anodes of Sodium-Ion Batteries

The formation of solid-electrolyte interphase (SEI) layers which results from the decomposition of organic solvents in the electrolyte on the anode of sodium-ion batteries (SIBs) is crucial and mus...

Stabilizing Capacity Retention of Li-Ion Battery in Fast-Charge by Reducing Particle Size of Graphite

Li plating at the graphite anode and the resultant reaction with electrolyte solvents is a mainstream mechanism for the performance degradation of Li-ion batteries in fast-charge. In this work, we assemble two-electrode and three-electrode graphite/LiNi0.8Co0.1Mn0.1O2 Li-ion cells with a relatively low cathode-to-anode capacity ratio to avoid Li plating, finding that the breakage of solid electrolyte interphase on the surface of the graphite anode and the resultant structural exfoliation of graphite and progressive decomposition of electrolyte solvents play a critical role in the performance degradation. Such breakage is suppressed by reducing the particle size of graphite. However, the reduction in the particle size of graphite does not show significant improvement on the charging rate capability of Li-ion cells because the LiNi0.8Co0.1Mn0.1O2 cathode is the rate-determining component. Owing to the weak Van der Waals forces between the layered graphene stacks of graphite, the large particle size of graphite can be easily reduced by increasing the milling time in the slurry-making process of the graphite electrode. The results of this work shed new insight into the performance degradation of Li-ion batteries in fast-charge, and suggest a direction for stabilization of capacity retention.

Synthesis of zeolite-templated carbons using oxygen-containing organic solvents

Zeolite-templated synthesis of ordered microporous carbons was performed with Ca 2+ ion-exchanged Y and beta zeolites, where the conventionally used carbon source gases ( e.g. , ethylene and propylene) were replaced by various organic solvents, such as methanol, ethanol, isopropanol, acetone, tetrahydrofuran, and diisopropyl ether. The oxygen-containing solvents were fed to the zeolites as carried by N 2 gas through a bubbler. Mass spectrometric analyses of the carbonization stream indicated that isopropanol, acetone, tetrahydrofuran, and diisopropyl ether were converted largely to propylene and H 2 O vapor, while ethanol and methanol to ethylene. The simultaneous generation of H 2 O and the olefins, without using high-pressure gas cylinders, can be merit in the Ca 2+ ion-catalyzed synthesis of zeolite-templated carbons (ZTCs). The approach in this work provides a facile way to produce high quality ZTCs exhibiting excellent micropore orders and high specific capacitances in supercapacitor applications. • Zeolite-templated carbon is obtained using common organic solvents as carbon sources. • In situ mass analysis reveals solvent decomposition into propylene, ethylene and H 2 O. • High-surface-area carbon exhibits high capacitance as a supercapacitor electrode.

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.

Effects of boric acid and water on the deposition of Ni/TiO2 composite coatings from deep eutectic solvent

Type III deep eutectic solvents (DES) have been extensively studied as a green electrodeposition solvent due to their wide potential window and degradability. The preparation of nickel-based coatings from DES commonly uses nickel chloride as the main precursor of Ni2+, but it generates harmful chlorides during long-term electrodeposition. This article uses nickel sulfate as the main precursor of Ni2+ to investigate the effects of boric acid and water on the deposition of Ni/TiO2 composite coatings from 1:2 choline chloride (ChCl) - ethylene glycol (EG) DES. It is found that light green Ni (OH)2 crystalline solid and solvent decomposition products such as trimethylamine appeared in the coating. Interestingly, the acidic environment created by boric acid can inhibit the formation of Ni(OH)2 and the decomposition of solvents. Moreover, adding water to DES can reduce its viscosity and increase its conductivity, which will speed up the reduction of nickel ions. Water can change the complex form of Ni2+ in DES and reduce the average crystallite size of the coating. In this paper, the mechanism of the effect of boric acid and water on the deposition behavior of Ni2+ in DES is analyzed, and the deposition model is established, which provides a theoretical and experimental reference for green preparation of composite coatings.