Precursors For Deposition Research Articles

Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH2CMe2CH2CH═CH2]2 in Solution and the Origin of Rapid Nucleation

The compound cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum, Pt[CH2CMe2CH2CH═CH2]2 (3), is a recently discovered chemical vapor deposition (CVD) precursor for the deposition of highly smooth pla...

A multi-layer Cu:Ga/In sputtered precursor to improve structural properties of CIGS absorber layer

A promising approach for depositing large area CIGS absorbers is the two-stage process, which involves preparation of Cu-In-Ga precursor films by sputtering and their subsequent high temperature annealing in Se containing atmosphere (selenization). Quality of the sputtered precursor film is one of the key factors in this method that defines the resulting quality of CIGS absorber after selenization. Present study describes a multi-layer approach for precursor deposition, wherein multiple thinner layers of Cu:Ga and In are sputtered in an alternating sequence to obtain a structurally and compositionally uniform precursor. The multi (10)-layer precursor shows notably improved structural and compositional uniformity compared to the 2-layer precursor. CIGS absorber made with 10-layer precursor exhibits a significantly better grain structure with a smooth surface morphology and uniform composition. Solar cell fabricated with this improved CIGS absorber shows an enhancement in light conversion efficiency compared to the cell with CIGS absorber made by selenization of 2-layer precursor.

Janus few layered graphene with asymmetric wettability as anti-flooding cathode supports in proton exchange membrane fuel cells

Water balance in cathode catalyst layer (CCL) is crucial for proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel strategy to develop a Janus few layered graphene particles (FLGP) with asymmetric wettability by varying the carbon precursors in the chemical vapor deposition (CVD) process. Using the Janus FLGP supported Pt with asymmetric wettability as the cathode of a PEMFC, a peak power density of 632 mW cm−2 was achieved, which was about two-folds of the hydrophobic FLGP and three-folds of hydrophilic FLGP based cathode, respectively. The enhanced performance could be ascribed to the well-constructed three-phase boundary in an anti-flooding cathode, leading to enlarged electrochemical active surface area and facilitated mass transfer. This work may provide new clues for improving water management in PEMFCs.

Photoelectrocatalytic improvement of copper oxide thin film fabricated using anodization strategy application in nitrite degradation and promoting oxygen evolution

This research is to develop Cu oxide thin film preparation using the anodization technique for the highest efficiency nitrite degradation and promoting oxygen evolution improvement. The electrochemical cell is developed by designing the electrode position to enhance the efficiency of Cu oxide thin film deposition on the anode electrode. The effects of precursor solution temperature, deposition time, and calcination temperature were studied to enhance the photoelectrocatalytic water reduction properties. The characteristics of the fabricated Cu oxide thin film were studied using scanning electron microscope, X-ray diffraction, and electrochemical impedance spectroscopy methods related to the photoelectrocatalytic activity improvement. The calcination temperature is a significant factor affecting physical properties, crystalline structure, morphology, and charge transfer rate, which relate to the photoelectrocatalytic activities. We have succeeded in developing the photoelectrocatalytic cell using the developed Cu oxide photocathode in cooperation with the FTO/WO3/BiVO4 photoanode for nitrite degradation and simultaneous oxygen production up to 98% and 6.0 mgO2/L for 120 min, respectively. This research is especially suitable for further development leading to a water treatment application that eliminates inorganic ions and increases the dissolved oxygen value in an aquarium system.

Study on Structural and Thermal Characteristics of Heteroleptic Yttrium Complexes as Potential Precursors for Vapor Phase Deposition

Yttrium oxide (Y2O3) thin films are implemented as a functional component in a broad field of applications such as optics, electronics or thermal barrier coatings. Atomic layer deposition (ALD) is a promising technique to fabricate high‐quality thin films with atomic level precision in which the precursor choice plays a crucial role in process development. The limited number of suitable yttrium precursors available for ALD of Y2O3 has triggered increasing research activity seeking new or modified precursors. In this study, heteroleptic compounds of yttrium bearing the cyclopentadienyl (Cp) ligand in combination with the chelating amidinate or guanidinate ligands were targeted as potential precursors for ALD. In this context, a systematic and comparative study of the structure and thermal characteristics of (bis‐cyclopentadienyl‐(N,N'‐diisopropyl‐2‐methyl‐amidinato)yttrium) [YCp2(dpamd)] 1 and (bis‐cyclopentadienyl‐(N,N'‐diisopropyl‐2‐dimethylamido‐guanidinato)yttrium) [YCp2(dpdmg)] 2 was performed. Complementary characterization tools such as 1H‐NMR, elemental analysis, electron‐impact mass spectrometry (EI‐MS) and single‐crystal X‐ray diffraction (XRD) confirmed the spectroscopic purity and the monomeric nature of the metalorganic compounds. Hirshfeld surface analysis revealed influence of the ligand choice on the intermolecular interactions of the compounds. The important figures of merit for a precursor, namely the thermal properties were investigated via thermogravimetric analysis. Thus, the volatility, transport behavior and thermal stability were examined and compared to their homoleptic counterparts [YCp3], [Y(dpamd)3] or [Y(dpdmg)3].

Characterization of Silicon Carbon Nitride for Low Temperature Wafer-to-Wafer Direct Bonding

Three-dimensional circuit integration in vertical stacking attracts significant attention as a promising technique to fabricate higher performance and multifunctional chips without current 2D scaling limitation. Generally, the 3D integration using micro bumps consisted of solder joints hold the major integration scheme. However, micro bumps using solders joints confront stacking issues in the case of finer pitch (> 2µm) due to misalignment during thermal compression bonding. The wafer-to-wafer (W2W) hybrid bonding system can be then introduced as one of the state-of-the-art techniques in the 3D integration scheme. In this bonding scheme, two different bonding combinations are established simultaneously, which are Cu-to-Cu and dielectric-to-dielectric, respectively. For these bonding structures, dielectric material adjacent to Cu is required as not only an insulator but also a mechanical factor to withstand the grinding process for further 3D integration. Silicon carbon nitride (SiCN) compound has aroused great interest for bonding dielectrics due to high thermal stability and strong bond strength for direct bonding as well as Cu diffusion barrier ability. Recently back-to-face W2W hybrid bonding using backside SiCN deposition are also challenging to DRAM applications. However, in the case of DRAMs stacking, SiCN W2W direct bonding must be processed at lower temperature (<250°C) due to memory assembly thermal budget although general W2W direct bonding including deposition step of dielectrics is performed at high temperature (>350°C). In the past, we have reported that low temperature bonding using SiCN film deposited at 370°C obtained more than 2.0 J/m2 of adhesion energy at 250°C of post annealing temperature. However, W2W direct bonding using SiCN film deposited at lower temperature (<250°C) have not been studied well. In this study, properties of W2W direct bonding with SiCN deposited at varied temperature are evaluated. Chemical and mechanical properties of SiCN film linked to the bonding quality are fundamentally studied by using specific measurements. The SiCN films were deposited by plasma enhanced chemical vapor deposition (PECVD) at specific temperature 200°C and 370°C. After deposition, these wafers were annealed in a 10% H2/N2 atmosphere at a temperature of 200°C. CMP with typical barrier metal slurry and pad was employed to flatten SiCN surface. Subsequently, the wafer surface was activated by using N2 plasma and rinsed in deionized water. Wafers were finally bonded at room temperature in the EVG GEMINI system. Different characterization techniques have been used to understand the layer quality of the SiCN film deposited at 200°C (which indicated as SiCN 200°C in the text) in comparison with the optimized SiCN deposited at 370°C (indicated as SiCN 370°C). Bond energies for the different wafer pairs have been calculated by using the blade insertion method. The highest bond energy ~ 2.3 J/m2 was obtained in the case of SiCN 370°C, while the bond energy for SiCN 200°C was ~ 1.4 J/m2. ERD observed the elemental composition in bulk for SiCN 370°C and 200°C, respectively (Table 1). It is found that SiCN 200°C is not pure SiCN as SiCN 370°C but it is characterized by the presence of oxygen into the bulk. Oxygen could come from absorbed moisture since deposition and annealing steps are including no oxygen resources. FTIR and XPS were carried out to clarify the chemical components of SiCN 370°C and SiCN 200°C (Figure 1). FTIR spectra of SiCN 200°C is compared with the spectra of SiCN 370°C in Figure 1(a). The broad peak 3100 – 3500cm-1 is assigned to N-H and O-H components, the last one due to moisture absorption from air ambient. A peak at ~1160 cm-1 can be assigned to NH3. This assignment is confirmed through XPS measurements where NH3 peak is detectable in the N1s peak (Figure 1 (c) right) while no NH3 peaks can be detected from the as-deposited SiCN 370°C (Figure 1(b) right). Such observation is suggesting the presence of residue of deposition precursors in the SiCN 200°C. In the Si2p peak of XPS spectra of Figure 1(c), it is observed that SiCN 200°C is characterized by less Si-C bonds compared to the SiCN 370°C as-deposited film. mainly Si-O bonds can be observed in the case of SiCN 200°C after N2 plasma while main peaks didn’t change from CMP for SiCN 370°C (Figure 2). The fact that in the as-deposited SiCN 200°C we do not have Si-C bonds is pointing to a missing desired property for the material since it was demonstrated that Si and C dangling bonds are essential in the process of enhancing bond energies. Figure 1

Anti-carbon deposition mechanism of H2O on nickel-based anode of SOFC: A ReaxFF molecular modelling

Carbon deposition occurs when Dimethyl ether (DME) fuel is used for SOFC, leading to battery degradation. In order to study the effect of water addition on carbon deposition, this work used reactive force field molecular dynamics (Reaxff MD) to simulate the process of carbon deposition with or without water addition, and analyze its anti-carbon deposition mechanism on nickel-based anode.It is found that the number of carbon atoms on nickel can be effectively reduced by mixing water with fuel. As the H2O/DME ratio increases, there are fewer carbon atoms on the nickel anode. And there are two main ways for water molecules to resist carbon deposition. First is that the OH group generated by decomposition of water molecules at high temperature reacts with CH component to form aldehyde group, which reduces the formation of carbon deposition precursor. The other is that the increase of water molecules introduces more oxygen atoms into the system, and the carbon atoms formed by DME molecules combine with oxygen atoms to form CO, thus reducing carbon deposition. This study is helpful to promote the industrialization of DME as SOFC fuel.

A Robust Method to Quantify Cell Wall Bound Phenolics in Plant Suspension Culture Cells Using Pyrolysis-Gas Chromatography/Mass Spectrometry.

The wide-scale production of renewable fuels from lignocellulosic feedstocks continues to be hampered by the natural recalcitrance of biomass. Therefore, there is a need to develop robust and reliable methods to characterize and quantify components that contribute to this recalcitrance. In this study, we utilized a method that incorporates pyrolysis with successive gas chromatography and mass spectrometry (Py-GC/MS) to assess lignification in cell suspension cultures. This method was compared with other standard techniques such as acid-catalyzed hydrolysis, acetyl bromide lignin determination, and nitrobenzene oxidation for quantification of cell wall bound phenolic compounds. We found that Py-GC/MS can be conducted with about 250 µg of tissue sample and provides biologically relevant data, which constitutes a substantial advantage when compared to the 50–300 mg of tissue needed for the other methods. We show that when combined with multivariate statistical analyses, Py-GC/MS can distinguish cell wall components of switchgrass (Panicum virgatum) suspension cultures before and after inducing lignification. The deposition of lignin precursors on uninduced cell walls included predominantly guaiacyl-based units, 71% ferulic acid, and 5.3% p-coumaric acid. Formation of the primary and partial secondary cell wall was supported by the respective ~15× and ~1.7× increases in syringyl-based and guaiacyl-based precursors, respectively, in the induced cells. Ferulic acid was decreased by half after induction. These results provide the proof-of-concept for quick and reliable cell wall compositional analyses using Py-GC/MS and could be targeted for either translational genomics or for fundamental studies focused on understanding the molecular and physiological mechanisms regulating plant cell wall production and biomass recalcitrance.

Enhanced interfacial reaction of precursor and low temperature substrate in HfO2 atomic layer deposition with highly Ar diluted O2 plasma

The internal energy of metastable oxygen atoms in highly Ar diluted oxygen plasma was utilized in the initial stage of the atomic layer deposition of HfO2 on SiO2/Si(100) at low temperature of 150 °C. The highly Ar dilute oxygen plasma enhanced the oxidation of the incomplete chemisorption state of the precursor at low temperature, successfully formed Hf silicate interface, and decreased the impurity nitrogen atoms in the HfO2 film compared to the pure oxygen plasma ALD. Residual nitrogen atoms in the film were found to cause excessive precursor adsorption. The results of plasma emission spectroscopy and ion saturation current measurements show that the highly Ar-diluted O2 plasma can increase the O radical formation rate for ion fluxes at pressures above 100 Pa. The relatively high metastable oxygen atom irradiation is thought to be responsible for the removal of HfN bonds and enable ALD on low temperature substrates. Atomic force microscopy showed that the root mean square roughness in the high Ar dilution sample was 0.093 nm, indicating high flatness.

The Instability of Monolayer-Thick PbSe on VSe2

Two-dimensional monolayers derived from 3D bulk structures remain a relatively unexplored class of materials because of the challenge of stabilizing nonepitaxial interfaces. Here, we report an unusual reconstruction during the deposition of precursors when targeting the synthesis of heterostructures with an odd number of PbSe monolayers. Multilayer elemental precursors of Pb|Se + V|Se were deposited to have the correct number of atoms to form [(PbSe)1+δ]q(VSe2)1 where q is the number of PbSe monolayers in the heterostructure. Structural analysis of the self-assembled precursor via X-ray reflectivity, X-ray diffraction, and HAADF-STEM suggests three different behaviors upon deposition. Precursors with q ≥ 7 and even values of q have the targeted nanoarchitectures after deposition, which are maintained as the products are self-assembled through a near diffusionless process. Significant lateral surface diffusion occurred during the deposition of precursors with q = 1, 3, and 5, resulting in the precursor to have a different nanoarchitecture than targeted. Additional perpendicular long-range diffusion occurs during self-assembly of these precursors, resulting in different final products than targeted. Density functional theory (DFT) calculations of PbSe blocks show that the odd-numbered layers are less stable than the even-numbered layers, which suggests an energetic driving force for the observed rearrangement. This work highlights the importance of understanding the reaction mechanism when attempting to prepare 2D layers of constituents with bulk 3D structures.

Preparation and properties of compositionally tunable Cu3Sb(Sx,Se1-x)4 thin films

In the paper, Cu3Sb(Sx,Se1-x)4 thin films were prepared by spin-coating method involving deposition of copper antimony sulfide precursor and then selenization of precursor in double-temperature zone space. The influence of selenium source temperature on properties of Cu3Sb(Sx,Se1-x)4 thin films was investigated. The phase structure, elemental composition, microstructure, optical and electrical properties were analyzed using appropriate characterization techniques. The results demonstrated Cu3Sb(Sx,Se1-x)4 thin films after selenization treatment had better crystallinity but Sb2Se3 impurity phase. The EDS analysis revealed that the Se concentration in the thin films increased with selenium source temperature. Morphological study indicated that the large grain appeared on the surface of thin films at higher selenium source temperature. The band gap of thin films linearly decreased with the increase of Se concentration. The as-prepared Cu3Sb(Sx,Se1-x)4 thin film showed p-type electrical behavior and an obvious photoconductivity.

In Situ Formation of CoMoS Interfaces for Selective Hydrodeoxygenation of p-Cresol to Toluene

Catalytic hydrodeoxygenation (HDO) of phenolics to aromatics is one of the most important reaction routes in bio-oil upgrading. Sulfided CoMo catalysts are good candidates for this reaction, but their activities are strongly associated with the number of exposed surface sites and Co–Mo synergy. Herein, we employ zeolitic imidazolate framework-67 as a cobalt precursor and template for inverse deposition of MoS2 ultrathin sheets inside the framework to form CoMoS interfaces by using a simple hydrothermal method. The size-confined MoS2 possesses a few-layered structure and abundant surface defects. It is found that in situ generation of a CoMoS active phase would take place to reach the best activity of our catalysts under the HDO reaction condition or by H2 prereduction treatment. With varying different Co–Mo molar ratios, the optimized CoMoS-0.18 catalyst exhibits the highest HDO activity, with a p-cresol conversion of 92.4% and a toluene selectivity of 95.5% at 250 °C. The high performance is ascribed to the formation of an accessible surface CoMoS phase after surface restructuring.

Inhibition of Colony-Stimulating Factor 1 Receptor by PLX3397 Prevents Amyloid Beta Pathology and Rescues Dopaminergic Signaling in Aging 5xFAD Mice.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease. In this study, to investigate the effect of microglial elimination on AD progression, we administered PLX3397, a selective colony-stimulating factor 1 receptor inhibitor, to the mouse model of AD (5xFAD mice). Amyloid-beta (Aβ) deposition and amyloid precursor protein (APP), carboxyl-terminal fragment β, ionized calcium-binding adaptor molecule 1, synaptophysin, and postsynaptic density (PSD)-95 levels were evaluated in the cortex and hippocampus. In addition, the receptor density changes in dopamine D2 receptor (D2R) and metabotropic glutamate receptor 5 were evaluated using positron emission tomography (PET). D2R, tyrosine hydroxylase (TH), and dopamine transporter (DAT) levels were analyzed in the brains of Tg (5xFAD) mice using immunohistochemistry. PLX3397 administration significantly decreased Aβ deposition following microglial depletion in the cortex and hippocampus of Tg mice. In the neuro-PET studies, the binding values for D2R in the Tg mice were lower than those in the wild type mice; however, after PLX3397 treatment, the binding dramatically increased. PLX3397 administration also reversed the changes in synaptophysin and PSD-95 expression in the brain. Furthermore, the D2R and TH expression in the brains of Tg mice was significantly lower than that in the wild type; however, after PLX3397 administration, the D2R and TH levels were significantly higher than those in untreated Tg mice. Thus, our findings show that administering PLX3397 to aged 5xFAD mice could prevent amyloid pathology, concomitant with the rescue of dopaminergic signaling, suggesting that targeting microglia may serve as a useful therapeutic option for neurodegenerative diseases, including AD.

Heat transfer studies of surface synthesized by chemical vapor deposition

In this paper, heat transfer characteristics of nickel coating over aluminium and mild steel are examined using jet impingement cooling. A rectangular sheet of dimension 10 cm × 3.5 cm × 0.1 cm taken as the test piece is coated with 4 g nickel acetate tetrahydrate precursor in the chemical vapor deposition (CVD) process for 85 mins. Heat transfer characteristics are studied on three layers of nickel coating (no coating, first coating, and second coating) with an impinging air-jet velocity of 3.5 ms−1 and 6 ms−1. The effect of Reynolds number, the thickness of the coating, jet velocity, distance from the stagnation point, and nozzle diameter on the heat transfer coefficient are investigated. The results show an increase in convective heat transfer characteristics with the Reynolds number, the thickness of the coating, and the nozzle diameter and a substantial decrease with deviation from the stagnation point.

Nanostructured Lead Sulphide Depositions by AACVD Technique Using Bis(Isobutyldithiophosphinato)Lead(II) Complex as Single Source Precursor and Its Impedance Study.

This communication reports the synthesis of bis(diisobutyldithiophosphinato)lead(II) complex and its subsequent application as a single source precursor for the nanostructured deposition of lead sulphide semiconductors and its impedance to explore its scope in the field of electronics. Synthesized complex was characterized by microelemental analysis, nuclear magnetic resonance spectroscopy, infrared spectroscopy and thermogravimetric analysis. This complex was decomposed using the aerosol-assisted chemical vapour deposition technique at different temperatures to grow PbS nanostructures on glass substrates. These nanostructures were analyzed by XRD, SEM, TEM and EDX methods. Impedance spectroscopic measurements were performed for PbS in the frequency range of 40 to 6 MHz at room temperature. In a complex impedance plane plot, two relaxation processes were exhibited due to grains and grain boundaries contribution. A high value of dielectric constant was observed at low frequencies, which was explained on the basis of Koops phenomenological model and Maxwell–Wagner type polarization. Frequency-dependent AC conductivity results were compliant with Jonscher power law, while capacitance–voltage loop had a butterfly shape. These impedance spectroscopic results have corroborated the ferroelectric nature of the resultant PbS nanodeposition.

Influence of precursor concentration and deposition temperature on the photoactivity of hematite electrodes for water splitting

Hematite nanoparticles were synthesized using chemical spray pyrolysis. Precursor concentrations of 30, 40, and 50 mM, deposition temperatures of 250, 340, and 400 °C were used. X-ray diffraction measurements confirmed the purity of hematite with no other phases of iron oxide. The (104) and (110) diffraction peaks associated with corundum structure of hematite were revealed in all the prepared thin films. The rhombohedral unit cell with space group R3¯C and average lattice constants, a = 5.042 Å and c = 13.673 Å were achieved. Scanning electron microscopy measurements obtained surface morphology of different grain sizes that ranged from 7 to 33 nm. From the UV–vis measurements, bandgaps that ranged from 2.10 to 1.92 eV for all films prepared at different precursor concentrations and temperatures were obtained. Photocurrent densities that ranged from 0.78 to 89 μA cm−2 were obtained for different precursor concentrations and deposition temperatures thin films. Further, all the samples had a donor density of 1018 cm−3 with a positive flat band potential in the range of 0.045 and 0.213 V.

Comparative Study of Strategies for Enhancing the Performance of Co3O4/Al2O3 Catalysts for Lean Methane Combustion

Spinel-type cobalt oxide is a highly active catalyst for oxidation reactions owing to its remarkable redox properties, although it generally exhibits poor mechanical, textural and structural properties. Supporting this material on a porous alumina can significantly improve these characteristics. However, the strong cobalt–alumina interaction leads to the formation of inactive cobalt aluminate, which limits the activity of the resulting catalysts. In this work, three different strategies for enhancing the performance of alumina-supported catalysts are examined: (i) surface protection of the alumina with magnesia prior to the deposition of the cobalt precursor, with the objective of minimizing the cobalt–alumina interaction; (ii) coprecipitation of cobalt along with nickel, with the aim of improving the redox properties of the deposited cobalt and (iii) surface protection of alumina with ceria, to provide both a barrier effect, minimizing the cobalt–alumina interaction, and a redox promoting effect on the deposited cobalt. Among the examined strategies, the addition of ceria (20 wt % Ce) prior to the deposition of cobalt resulted in being highly efficient. This sample was characterized by a notable abundance of both Co3+ and oxygen lattice species, derived from the partial inhibition of cobalt aluminate formation and the insertion of Ce4+ cations into the spinel lattice.

Vapor-liquid-solid-like growth of thin film SiC by nanoscale alternating deposition of SiC and NiSi2

We propose a vapour-liquid-solid (VLS)-like growth by alternately depositing nanoscale precursors of film and liquid flux using a pulsed laser deposition system with rapid beam deflection (RBD-PLD). The nanoscale alternating deposition of NiSi2and SiC precursors on a 4H-SiC substrate at 1000 °C was found to suppress the formation of stacking faults and the carbon aggregates in the fabricated SiC films. As a result, the growth of high-quality 3C-SiC films having a flat surface with a step-and-terrace structure was achieved under the optimized conditions.The advantage of this process is that the required amount of the NiSi2flux can be much reduced as compared to in the conventional VLS process; e.g., it could be as small as 5 vol% in volume ratio to the thin film SiC in the present case.The high crystallinity of the fabricated 3C-SiC thin films was also supported by their high visible photocurrent responseratio.Themechanism of the vapour-liquid-solid (VLS)-like growth is also discussed.

Sustainable Cu2ZnSnSe4 photovoltaic cells fabricated with a sputtered CdS buffer layer

AbstractIn this study, the effect of the Cu concentration on the characteristics of the Cu2ZnSnSe4 (CZTSe) absorber layers and solar cells was systematically analyzed by postselenization of the evaporated precursor deposits. The results demonstrated that an increase in the copper concentration of the precursor linearly increased the Cu content in the final CZTSe thin‐film formation. This significantly increased the particle size and improved the re‐evaporation loss of the SnSe, thus improving the solar cell characteristics. However, a further increase in the Cu concentration reduced the quality of the absorber layer and formed either CuxSe or CTSe secondary phases, which was detrimental to the solar cell characteristics. Here, we introduce a sputtered CdS buffer layer for the CZTSe solar cells. These findings offer new research directions for solving the persistent challenges in the chemical bath deposition (CBD) of the CdS in the CZTSe solar cells.

Promoted Deposition of Three-Dimensional Li2S on Catalytic Co Phthalocyanine Nanorods for Stable High-Loading Lithium-Sulfur Batteries.

The sulfur redox in Li-S batteries involves a complex sequence of solid-liquid-solid conversions, and reaction catalysis has recently become a focused area for further advancement. The deposition of solid Li2S from liquid Li2S4 contributes to three-quarters of the total theoretical capacity and is therefore of great significance over the entire cathode reaction. This study demonstrates a cathode material composed of carbon nanofibers decorated with catalytic Co phthalocyanine nanorods (CoPc@CNF), which are highly effective in promoting the deposition of Li2S in three-dimensional (3D) fine particles rather than 2D thin films. This significantly alleviates cathode passivation during cell charge and discharge, leading to obviously improved sulfur utilization and cycling stability for high loading cathodes. DFT calculations indicate that the promoted 3D deposition of Li2S is related to the facilitated migration of deposition precursors (Li2S4 and Li-ions) to migrate on the CoPc nanorods. Lithium-sulfur (Li-S) pouch cells were prepared with high specific (954 mAh g-1), areal (4.8 mAh cm-2), and total (235 mAh) capacities achieved at 0.5 C under high sulfur content. As metal phthalocyanines possess a high structural variability, this study provides opportunities to the design of a new class of Li-S cathode materials.