Layer-structured Materials Research Articles

Destabilization of the surface structure of Ni-rich layered materials by water-washing process

Washing Ni-rich layered materials with water is a simple and effective way to reduce gas evolution by eliminating the gas generation factors. However, the water-washing process itself degrades the electrochemical performances; hence additional treatments such as heating and coating are undertaken. Thus, most studies for the post-process mainly focus on the relationship between additional treatments and electrochemical performances, not paying much attention to the water-washing effect. Here, we focused on the effect of water-washing on the Ni-rich layered materials by studying bare and water-washed LiNi0.88Co0.054Mn0.066O2(NCM) cathodes. The results of synchrotron-based X-ray analysis indicate that the crystal and electronic structures are the same in the bulk aspect after the water-washing process, but differences occur in the surface environment. The amount of Li2CO3 decreases while NiO-like rock-salt phase increases on the surface of the water-washed NCM, and it deteriorates the rate performances by elevating the surface resistances. Furthermore, the surface layer reconstruction of water-washed NCM, which has lower capacity retention during 200 cycles, is much more severe than the bare NCM; this indicates that the water-washing process makes the surface of Ni-rich layered materials more vulnerable to the side reaction, facilitating the formation of NiO-like rock-salt phase by the reconstruction.

Investigation on the structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 modified with Sn

Ni-rich layered cathode materials are promising cathode materials for lithium-ion batteries with high energy density. To reveal the influence of Sn-coating and doping on the structure and electrochemical performances of Ni-rich layered cathode materials, LiNi0.8Co0.1Mn0.1O2, LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) are designed and synthesized. The effect of lithium-tin-oxide coating and Sn-doping on the structural and electrochemical behavior of Ni-rich cathode material are compared and investigated. Compared with the bare LiNi0.8Co0.1Mn0.1O2 cathode material, both LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and Sn-doped LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) samples exhibit better electrochemical performances. The capacity retention for Li2SnO3-coated and Sn-doped materials after 270 cycles at 0.5C can reach as high as 93.7 and 96.6%, respectively. Besides, improved rate capabilities and thermal stability are also obtained for Li2SnO3-coated and Sn-doped materials. The superior electrochemical performances and enhanced thermal stability of Li2SnO3 coated samples are mainly ascribed to the higher interfacial stability and those of Sn-doped materials may be mainly due to higher structural stability and lower polarization than those of the bare LiNi0.8Co0.1Mn0.1O2 cathode material. These results indicate that the introduction of Sn ions, especially Sn doping, may be an effective strategy to improve the performance of Ni-rich layered cathode materials.

A reversible tuning of Fermi level in BiSbTe3 thin films through ion implantation

In layered structure materials, tuning of strain is used to control critical electronic and physical properties. In this work, precise and controlled tuning of strain is achieved with implantation. Thin films of BiSbTe3 were implanted with Fe ion of energy 100 keV at 5 different fluences. The lattice strain is found to be reversibly tuned with Fe implantation. The effect of Fe ions on the electronic band structure of BiSbTe3 is confirmed by the change in resistivity and tuning of Fermi level with implantation. The observed reversible tuning of the Fermi level suggests the possibility of device control applications.

Effects of inter/intralayer adsorption and direct/indirect reaction on photo-removal of pollutants by layered g-C3N4 and BiOBr

Photocatalysis is an effective process to utilize solar energy for contaminants degradation, and the catalytic performance depends on the intrinsic structural properties of catalysts and organic molecules as well as their interactions. This work innovatively reveals that layer-structured graphitic carbon nitride (GCN) and BiOBr exhibit distinctly different adsorption and photocatalytic behaviors and that they show respective advantages in catalytic removals of Congo red (CR) and ibuprofen (IBP). The kinetic rate constant of CR removal by GCN was about 1.3 times higher than that by BiOBr, while BiOBr has a superior photocatalytic degradation performance towards IBP with a 25-fold-higher kinetic rate constant than that of GCN. Experiments including temperature-controlled adsorption and degradation as well as mechanism discussion confirmed that IBP and CR could be strongly adsorbed in the surface intralayer of BiOBr and GCN, through unique coordination interaction, while CR adsorption on BiOBr was dominated by interlayer adsorption. Thermodynamically, we examine that these layered catalysts can induce different reactive species according to their unique valence band and conduction band locations and then trigger different oxidation pathways for degradation reaction, as confirmed by the quenching experiments. Depending on the dissociated superoxide (O2•−) radical induced indirect oxidation pathway, GCN has higher kinetics for CR degradation than BiOBr. In contrast, BiOBr offers better photocatalytic performance for IBP degradation through the direct oxidation pathway of photogenerated holes (h+). BiOCl, with an analogous structure to BiOBr, also exhibits a similar behavior to BiOBr. This work provides a new perspective for understanding the different behaviors of layer-structured materials in selective oxidation of pollutants.

Влияние циклической термической обработки на структуру слоистого композиционного материала из стали марок 08кп и 08Х18Н10

The article researches the effect of five cycles of heating to a temperature of 1000 °C and two cycles of heating to a temperature of 1100 °C on the structure of a layered composite material consisted of 100 alternating layers of 08kp and 08Kh18N10 steels (one layer thickness is ~22 μm). As a result of the nickel and chromium diffusion during thermocycling, the thickness of the layers changed and an interlayer with a structure different from the structure of neighboring layers was formed. Heating to 1100 °C also has led to a partial disarrangement of the layered material structure. It was found that the real diffusion path of alloying elements during heat treatment significantly exceeds the calculated one, and chromium atoms are redistributed between the layers of the material much more actively than nickel atoms.

Ab initio investigations on metal ion pre-intercalation strategy of layered V2O5 cathode for magnesium-ion batteries

Metal ions pre-intercalated layered structure materials are considered as potential high performance cathodes for Mg-ion batteries (MIBs). Herein, metal ions pre-intercalation strategy of layered cathode for MIBs by using Li, Na, Al pre-intercalated V2O5 cathode as a carrier has been investigated and proposed based on first principle calculations. The pre-intercalation process is energetically favorable and metal ion pre-intercalation improves the electronic conductivity of V2O5. The bondings of Li-V2O5, Na-V2O5 and Al-V2O5 all exhibit ionic characters, and the interaction between Al ion and V2O5 is the strongest. The interlayer distance expansion of Na pre-intercalated V2O5 is more trivial than that of Li, Al pre-intercalated V2O5. The open circuit voltage of the V2O5 cathode is dropped by pre-intercalated metal ions, and the voltage of Li and Na pre-intercalated V2O5 is higher than that of Al pre-intercalated V2O5. The diffusion barriers of Mg in the V2O5 matrix are reduced by pre-intercalation. Overall, metal ion pre-intercalation with a large atomic radius and small atomic charges holds great potentials to expand interlayer distance, enhance electronic conductivity, maintain high discharge voltage and improve diffusion ability of layered cathode. We hope our work could provide a significant guidance to the practical design of layered cathodes for MIBs.

Effects of La and Ni doping on ferroelectric and photocatalytic properties of Aurivillius Bi7Ti3Fe3O21

Bismuth layered structure materials with Aurivillius phase usually show amazing structure and physical properties. The influence of La and Ni doping on the structure, ferroelectricity and photocatalytic performance of Bi7Ti3Fe3O21 (BTF), Bi5.6La1.4Ti3Fe3O21 (La: BTF), Bi7Ti3Fe2.4Ni0.6O21 (Ni: BTF) and Bi5.6La1.4Ti3Fe2.4Ni0.6O21 (La, Ni: BTF) ceramics are explored. The enhancement of La: BTF ferroelectricity is due to the reduction of leakage current and oxygen vacancies. Co-doped La, Ni: BTF has the highest degree of ferroelectric polarization due to the large distortion of the lattice structure. La: BTF has the highest photocatalytic degradation efficiency for methylene blue (MB) dye. The reduction of grain radius, band gap and enhancement of ferroelectric polarization play a vital role in improving photocatalytic efficiency. Ni doping suppresses photocatalysis of BTF to some extent.

Fast synthesis of MoO3-x and its catalytic effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (DAP-4)

In this work, it is shown that MoO3-x has a positive effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (H2DABCO)[NH4(ClO4)3] (DAP-4). MoO3-x was prepared by heat treatment, and the morphology, structure, and thermal decomposition performance were characterized. The morphology and structure characterization results showed that MoO3-x was an irregular layered structure material and the Mo element was mainly in the +6 chemical valence state, with a small amount of Mo5+. Thermal analysis results showed that the thermal decomposition peak temperature of DAP-4 was effectively reduced from 394.4 °C to 353.7 °C, 321.4 °C, and 312.5 °C in the presence of 1%, 5%, and 10% MoO3-x, respectively. It is particularly worth noting that the maximum heat release rate of the DAP-4/10% MoO3-x mixture was increased by 4.9 times compared with pure DAP-4. Through the two classic thermal decomposition kinetic methods, Kissinger and Starink, the reliable kinetic parameters of DAP-4/MoO3-x were obtained. The increase of the reaction rate constant k indicated that the maximum thermal decomposition reaction rate of DAP-4 was effectively improved. This work provided a feasible technology for using MoO3-x as an effective catalyst to improve the thermal performance of DAP-4.

The Role of Alkali Cation Intercalates on the Electrochemical Characteristics of Nb2 CTX MXene for Energy Storage.

The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li+ -, Na+ -, and K+ -based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb2 CTx electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li2 SO4 , Na2 SO4 , and K2 SO4 electrolytes with d-spacing. Additionally, our results showed that the Nb2 CTx electrode exhibited higher electrochemical performance in the presence of Li2 SO4 than in that of Na2 SO4 and K2 SO4 . This is partly because the smaller-sized Li+ transports quickly and intercalates between the layers of Nb2 CTx easily. Poor ion transport in the Na2 SO4 electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li+ >Na+ >K+ . Our experimental studies provide direct evidence for the intercalation mechanism of Li+ , Na+ , and K+ on the 2D layered Nb2 CTx electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes.

P‐16.15: Research on Corrosion Prevention of Touch panel

In this paper, metal trace corrosion in the process of touch panel reliability evaluation was analyzed. The impact of different layer structure, membrane thickness and trace material on corrosion resistance of products was studied. First, scanning electron microscope (SEM) was used to analysis microstructure of corrosion trace cross section, and uv‐vis spectrophotometer, ion chromatograph was used to analysis corrosion product chemical composition, the cause of trace corrosion was analyzed. Then, the impact of environmental humidity, trace material, OC2 film thickness, secondary black matrix coverage, SiOxNy layer on corrosion resistance of trace was studied. Experimental results indicate that humidity is the necessary condition to corrosion, corrosion does not occur when humidity is zero. The corrosion resistant ability of Aluminum alloy than pure aluminum. Increase the film thickness, enhancement secondary black matrix coverage, add SiOxNy layer can greatly increase the corrosion resistant ability of the product.

Preparation and Sound Absorption Properties of MPP-polymers Layered Structure Materials

Preparation and Sound Absorption Properties of MPP-polymers Layered Structure Materials

Effects of transition metal doping on electrochemical properties of single-crystalline LiNi0.7Co0.1Mn0.2O2 cathode materials for lithium-ion batteries

Layer Ni-rich cathode material has been attracted much attention due to its high energy density. A critical challenge of Ni-rich LiNi1−x-yCoxMnyO2 systems is the severe capacity fading and poor rate capability due to the structural degradation during lithium-ion battery (LIB) cycle process. In this study, we employ a fast screening methodology to determine the effects of doping single-crystalline LiNi0.7Co0.1Mn0.2O2 with cations Nb5+, Sr2+, Y3+, and then focus on the effects of Nb-ion doping on the structural stabilization (Nb-NCM). Nb ions doping and single crystallization are applied for LiNi0.7Co0.1Mn0.2O2 (Nb-NCM), which enhance the structural stability and upgrade the electrochemical performance. Impressively, the modified Nb-NCM material shows remarkably cycling at the rate of 1 C (3.0–4.5 V) with a capacity retention of 80.1% after 200 cycles. Even at high temperatures (45 ℃), the structure of Nb-NCM also remains stable, which has a capacity of 149.8 mA h g−1 at 1 C (3.0–4.5 V) after 100 cycles. Further studies reveal that the successful doping of Nb-ion effectively inhibits cation mixing degree and structural degradation, and increases the diffusion coefficient of lithium-ion, which is the key to obtain the excellent electrochemical performance for LIBs. The present work indicates that the method of Nb-ion doping single-crystalline particles is an effective strategy to improve the stability of layered structure of Ni-rich NCM cathode material, and it represents an improve advance in the development of outstanding performance lithium-ion batteries.

Atomistic Observation of Desodiation-Induced Phase Transition in Sodium Tungsten Bronze.

The phase instability in layered-structure Na0.5WO3.25 induced by the extraction of Na ions was investigated by applying transmission electron microscopy. Real-time atomic-scale observation reveals the phase transition pathway: Na0.5WO3.25 (triclinic) → NaxWO3 (cubic) → WO3 (monoclinic) with specific orientation relationships. The dynamic evolution of Na0.5WO3.25/NaxWO3 phase boundaries shows that Na0.5WO3.25 will cleave along the (100)T and (010)T and recrystallize as (101)C and (010)C of NaxWO3, respectively. The phase transition pathway can be well-explained according to the structural characteristics in the three phases. By better understanding of the phase instability induced by the extraction of Na ions in possible layered-structure cathode materials, this work provides a reference for the design of sophisticated strategies toward high-performance Na-ion batteries.

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Stabilizing Ni-Rich LiNi0.83Co0.12Mn0.05O2 with Cyclopentyl Isocyanate as a Novel Electrolyte Additive

Ni-rich layered structure materials are appealing cathodes for high-energy-density lithium-ion batteries developed for electric vehicles, drones, power tools, etc. However, poor interfacial stability between a Ni-rich cathode and carbonate electrolyte, especially at high temperatures, and fast capacity fading still hinder their mass market penetration. Here, we investigate cyclopentyl isocyanate (CPI) with a single isocyanate (-NCO) functional group as a bifunctional electrolyte additive for the first time to improve the interfacial stability of Ni-rich cathode LiNi0.83Co0.12Mn0.05O2 (NCM83). With an electrolyte containing 2 wt % CPI, the NCM83 cathode shows capacity retention of up to 92.3% after 200 cycles at 1C and 30 °C, much higher than that with the standard electrolyte (78.6%). It is demonstrated that the -NCO of CPI could largely inhibit the thermal decomposition of LiPF6 salt and scavenge water and hydrogen fluoride (HF) species, improving electrolyte stability. More importantly, the additive CPI could be preferentially oxidized, forming a stabilized and protective cathode electrolyte interphase (CEI) layer on the surface of NCM83, which effectively suppresses the parasitic side reactions and maintains the superior interfacial charge-transfer and lithium-ion diffusion kinetics. Both functions enable a significant improvement in electrochemical performance at both 30 and 60 °C.

Controllable preparation of Fe-containing Li-rich cathode material Li[Li1/5Fe1/10Ni3/20Mn11/20]O2 with stable high-rate properties for Li-ion batteries

Generally, the optimization of synthesis conditions has great influence on the properties of the electrode materials for lithium-ion batteries (LIBs). Nowadays, Li-rich manganese-based cathode materials with high capacity are still suffering from low first charge/discharge capacity and poor high-rate capability. In this work, Li[Li[Formula: see text]Fe[Formula: see text]Ni[Formula: see text]Mn[Formula: see text]]O2 has been successfully synthesized by hydroxide co-precipitation method, and the effect of calcination temperature on the material characteristics and electrochemical performance has been investigated. The results show that with the increase of calcination temperature, the layered structure of Li-rich material becomes better. When the calcination temperature is 800[Formula: see text]C, the prepared material exhibits the most excellent electrochemical properties, including high first charge/discharge specific capacity of 366.6/251.9 mAh g[Formula: see text] and good high-rate capability. It is expected that the results of this study can lay a solid foundation for the subsequent research on the modification of this material.

Tailoring the optical properties of SrBi4Ti4O15 thin films by RF sputtering process parameters

SrBi4Ti4O15 is a bismuth layered perovskite structure material, its thin film form gained much interest due to their geometrical flexibility and thickness. In the present study, SrBi4Ti4O15 thin films are deposited on amorphous substrate using radio frequency sputtering technique. SrBi4Ti4O15 thin films found to be single phase orthorhombic structure by using X-ray diffraction technique. Surface morphology studies such as grain size, shape and roughness were explored through atomic force microscopy. EDX analysis identified the individual elements and its percentage in the compound. Optical properties (refractive index and bandgap) were determined with varying the oxygen mixing percentage (OMP). The best optical properties (refractive index ~ 2.35 and bandgap ~ 3.4 eV) were obtained for films deposited at 50% OMP. These results shows the potential of using SrBi4Ti4O15 thin films in electro-optic devices.

Understanding the Ni-rich layered structure materials for high-energy density lithium-ion batteries

The development of electric and hybrid electric vehicles has emerged as one of the most promising strategies for solving the global shortage of fossil energy problem.

Thermoelectric performance enhancement by manipulation of Sr/Ti doping in two sublayers of Ca3Co4O9

Thermoelectric (TE) performance of Ca3Co4O9 (CCO) has been investigated extensively via a doping strategy in the past decades. However, the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system. In this work, Sr and Ti are chosen to realize doping at the [Ca2CoO3] and [CoO2] sublayers in CCO. It was found that figure of merit (ZT) at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO. The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co4+ originating from the Sr doping effects in [Ca2CoO3] sublayer, which are evidenced by the scanning electron microscope (SEM), Raman, Hall, and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in [Ca2CoO3] sublayer. Our findings demonstrate that doping at Ca sites of [Ca2CoO3] layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient, and reducing the thermal conductivity simultaneously. This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.

Sn stabilized pyrovanadate structure rearrangement for zinc ion battery

Abstract Rechargeable zinc-ion batteries (ZIBs) have shown great potential for grids-level energy storage system. However, the lack of desirable and stable cathode materials remains challenging. Herein, Sn1.5V2O7(OH)2•3.3H2O, in which pyrovanadate V2O74− group pillared with Sn oxide layer, is developed as an advanced cathode for ZIBs and a hidden reaction mechanism in SnVO cathode through in-situ Raman and ex-situ XANEs, involves the opening of V˭O edge bonding and formation of Sn–O–V bonding, which leads to charge screening effect and facilitates the fast diffusion kinetics for zinc ions, as quantitatively verified by kinetic analysis. Additionally, the tetravalent Sn ions bring about stronger ionic bonds, binding to pyrovanadate V2O74− group and leading to good stability in the pyrovanadate framework, which guarantee the cycling stability. As a result, the as-prepared SnVO shows long cycling life as well as excellent rate capability. We demonstrate that, even cycled at high current of 10 A/g, the SnVO cathode can still retain a capacity of 130 mAh/g for over 500 cycles, indicating remarkable high capacity at high rate. Our findings reveal that the tetravalent tin ions have a strong beneficial effect on the battery performance of the layered-structure cathode materials. It is believed that our study would boost further studies in other multi-valent rechargeable batteries.