O2 Particles Research Articles

Influence of graphene wrapped-cerium oxide coating on spherical LiNi0.5Mn1.5O4 particles as cathode in high-voltage lithium-ion batteries

Cobalt-free LiNi 0.5 Mn 1.5 O 4 (Lithium Nickel Manganese Oxide; LNMO) has garnered considerable interest as a cathode material due to its high working voltage, lower cost, and environmental friendliness. However, LNMO cathodes currently exhibit low cyclability and capacity deterioration, severely restricting their use on a broader scale. To this end, microwave-assisted chemical co-precipitation was used to produce spherical aggregated nanoparticles of LiNi 0.5 Mn 1.5 O 4 (LNMO) coated with CeO 2 (LNMO-Ce) and wrapped in graphene (LNMO-Ce-GO). Structural analysis demonstrates that the ceria coating along with the graphene wrapping prevents unwanted phases from forming and altering the morphology of the LNMO microspheres. LNMO-Ce-GO exhibits a discharge capacity of 132.4 mAhg −1 at the C/10 rate with a capacity retention of 95.3 % after 100 cycles, compared to LNMO-Ce and bare LNMO samples that provide a capacity retention of 91.6 % and 84.7 % respectively. DSC analysis elucidate that the ceria coating helps to suppress the adverse reactions at the electrode/electrolyte interface and reduce the Mn 3+ dissolution due to the Jahn Teller effect, increasing cell cyclability. The graphene wrapping reduces material aggregation and provides conductive pathways that significantly improve the electrochemical performance of the LNMO cathode. This innovative material design strategy can be efficiently expanded to other classes of lithium-ion battery cathode materials to enhance their electrochemical performance. • Graphene wrapped ceria coated LiNi 0.5 Mn 1.5 O 4 was synthesized utilizing microwave-assisted chemical co-precipitation technique. • SEM analysis illustrates the formation of secondary spherical microspheres with primary nanoparticles of LiNi 0.5 Mn 1.5 O 4 . • TEM analysis exhibits a 1–3 nm ceria coating and graphene wrapping over LiNi 0.5 Mn 1.5 O 4 particles. • Surface-modified disordered LNMO exhibits improved cyclability with a 98.6 % capacity retention after 100 cycles at C/10 rate. • Graphene wrapping & ceria coating reduces interfacial resistance and increases lithium-ion diffusion kinetics.

Synthesis of Micron-Sized LiNi0.8Co0.1Mn0.1O2 and Its Application in Bimodal Distributed High Energy Density Li-Ion Battery Cathodes

The uniform and smaller-sized (~3 μm) LiNi0.8Co0.1Mn0.1O2 (SNCM) particles are prepared via a fast nucleation process of oxalate co-precipitation, followed by a two-step calcination procedure. It is found that the fast nucleation by vigorous agitation enables us to produce oxalate nuclei having a uniform size which then grow into micron-particles in less than a few minutes. The impacts of solution pH, precipitation time, calcination temperature, and surface modification with ZrO2 on the structural, morphological, and electrochemical properties of SNCM are systematically examined to identify the optimal synthetic conditions. A novel bimodal cathode design has been highlighted by using the combination of the SNCM particles and the conventional large (~10 μm) LiNi0.83Co0.12Mn0.05O2 (LNCM) particles to achieve the high volumetric energy density of cathode. The volumetric discharge capacity is found to be 526.6 mAh/cm3 for the bimodal cathode L80% + S20%, whereas the volumetric discharge capacity is found to be only 480.3 and 360.6 mAh/cm3 for L100% and S100% unimodal, respectively. Moreover, the optimal bi-modal cathode delivered higher specific energy (622.4 Wh/kg) and volumetric energy density (1622.6 Wh/L) than the L100% unimodal (596.1 Wh/kg and 1402.1 Wh/L) cathode after the 100th cycle. This study points to the promising utility of the SNCM material in Li-ion battery applications.

Transport Properties in Electrodes for Lithium-Ion Batteries: Comparison of Compact versus Porous NCM Particles

Previous investigations on porous Li(NixCoyMnz)O2 (NCM) particles with shortened diffusion paths and an enlarged interface between active material and electrolyte show improved rate capability and cycle stability compared to compact particles. Due to the additional intragranular porosity of the active material, also the pore structure of the overall electrode, and as consequence, the ionic transport in the pore phase is altered. In addition, the particle morphology influences the ohmic contact resistance between the current collector and electrode film. These effects are investigated using impedance spectroscopy in symmetrical cells under blocking conditions. The ionic resistance and the tortuosity of the electrodes are determined and analyzed by a transmission line model. Tortuosity is higher for porous particles and increases more during calendering. This limits the options to densify these electrodes to the same level as with compact particles. In a further approach, the method is used to explain the drying related performance differences of these electrodes. At higher drying rates, the contact and the ionic resistance of electrodes with compact particles increases more strongly as for electrodes with porous particles. These investigations provide new insights into the ion transport behavior and enable a better understanding of the impact of the electrode processing condition.

Microscopic insight into catalytic HCN removal over the CuO surface in chemical looping combustion

Hydrogen cyanide (HCN) is well-accepted as a main nitrogen-containing precursor from fuel nitrogen to nitrogen oxides. When using coal as fuel with a CuO-based oxygen carrier in chemical looping combustion (CLC), complex heterogeneous reactions exist among the system of HCN, O2, NO, H2O, and CuO particles. This work performs density functional theory (DFT) calculations to systematically probe the microscopic HCN heterogeneous reactions over the CuO particle surface. The results indicate that HCN is chemisorbed on the CuO surface, and the third dissociation step within the consecutive three-step HCN dissociations (HCN*→CN*→NCO*→N*) is the rate-determining step. Namely, the CN*/NCO* radicals can be deemed as an indicator of the performance of HCN removal due to their quite higher dissociation energies. With the existence of O2, H2O, and NO, the reaction mechanism of HCN conversion becomes extremely complex. Both DFT calculations and kinetic analyses determine that O2, NO, and H2O all significantly accelerate the consumption of CN*/NCO* radicals to produce various N-containing species (NOx or NH3) to different extents. Finally, a skeletal reaction network in a system of O2/NO/H2O/HCN is concluded, which clearly elucidates that CuO exhibits excellent catalytic activity toward HCN removal.

Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like NiAl-LDH microspheres with Z-scheme for significantly enhanced CO2 photoreduction into CO

The conversion of carbon dioxide (CO2) into value-added C1 and/or C2 chemicals by photocatalytic technology has been regarded as a “one stone-two birds” solution for environmental degradation and energy shortage. In this work, a novel Z-scheme mechanism photocatalyst of Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like layered nickel-aluminum hydroxides (NiAl-LDH) microspheres (α-Fe2O3/Ag/NiAl-LDH, designated as FALDH) is successfully prepared by a combined in-situ hydrothermal and grating strategy. As expected, the optimal sample of FALDH-5/10 exhibits significantly enhanced photocatalytic performance for CO2 reduction with a highest CO yield up to 46.7 μmol g−1 under simulated sunlight without any sacrificial reagents and photosensitizers, compared with the pristine NiAl-LDH, binary Ag/NiAl-LDH and α-Fe2O3/NiAl-LDH, as well as surpassing the previously reported LDH-based counterparts. The high activity is ascribed to strong interaction between the NiAl-LDH microspheres and highly-dispersed Ag/α-Fe2O3 particles, boosted CO2 adsorption capacity and optimized bandgap from α-Fe2O3, and increased utilization efficiency of light from Ag. This study offers a new idea for more efficient stimulating the photocatalytic activity of LDHs by the construction of Z-scheme heterojunction with the aid of plasmonic metal(s) for CO2 photoreduction, and is expected to be employed to other photocatalytic applications effectively.

Enhanced Electrochemical Capacity of Spherical Co-Free Li1.2 Mn0.6 Ni0.2 O2 Particles after a Water and Acid Treatment and its Influence on the Initial Gas Evolution Behavior.

Li-rich layered oxides (LRLO) with specific energies beyond 900 Wh kg-1 are one promising class of high-energy cathode materials. Their high Mn-content allows reducing both costs and the environmental footprint. In this work, Co-free Li1.2 Mn0.6 Ni0.2 O2 was investigated. A simple water and acid treatment step followed by a thermal treatment was applied to the LRLO to reduce surface impurities and to establish an artificial cathode electrolyte interface. Samples treated at 300 °C show an improved cycling behavior with specific first cycle capacities of up to 272 mAh g-1 , whereas powders treated at 900 °C were electrochemically deactivated due to major structural changes of the active compounds. Surface sensitive analytical methods were used to characterize the structural and chemical changes compared to the bulk material. Online DEMS measurements were conducted to get a deeper understanding of the effect of the treatment strategy on O2 and CO2 evolution during electrochemical cycling.

Improving the electrochemical performance of single crystal LiNi0.5Mn1.5O4 cathode materials by Y–Ti doping and unannealing process

In recent years, due to the rising price of cobalt, people have been increasingly interested in LiNi0.5Mn1.5O4 (LNMO) cathode materials, and many studies researches have been carried out on the preparation and modification of LNMO. However, the codoping of Y and Ti and the choice of annealing and unannealing processes after doping are less explored. In this study, single-crystal LNMO particles and Y, Ti-doped LiNi0.45Mn1.45O4 particles were prepared by a simple sol-gel method under annealing and unannealing processes, respectively. Four samples were analyzed by X-ray powder diffraction, Raman spectra, Fourier transform infrared spectroscopy and electron paramagnetic resonance. By these means, it was found that the samples doped and not annealed had the largest amount of disordered structures and oxygen vacancies (OVs). Scanning electron microscopy showed that the doped and unannealed samples had more exposed (100) crystal planes than the other samples, and after multiple cycles, this sample had the smoothest surface morphology. Electrochemical tests show that the doped and unannealed samples exhibit excellent electrochemical performance, with a Coulombic efficiency of 93.94% in the first cycle, a specific capacity of 126.74 mAh⋅g−1 after 500 cycles at a rate of 1 C, and a specific capacity of 126.74 mAh⋅g−1 at a rate of 5 C. After 500 cycles, the specific capacity is 111.1 mAh⋅g−1.

Which Exchange Current Densities Can Be Achieved in Composite Cathodes of Bulk-Type All-Solid-State Batteries? A Comparative Case Study.

The performance of bulk-type all-solid-state Li batteries (ASSBs) depends critically on the contacts between cathode active material (CAM) particles and solid electrolyte (SE) particles inside the composite cathodes. These contacts determine the Li+ exchange current density at the CAM | SE interfaces. Nevertheless, there is a lack of experimental studies on Li+ exchange current densities, which may be caused by the poor understanding of the impedance spectra of ASSBs. We have carried out a comparative case study using two different active materials, namely, single-crystalline LiCoO2 particles and single-crystalline LiNi0.83Mn0.06Co0.11O2 particles. Amorphous 0.67 Li3PS4 + 0.33 LiI particles act as a solid electrolyte within the cathode and separator, and lithiated indium acts as the anode. The determination of the cathode exchange current density is based on (i) impedance measurements on In-Li | SE | In-Li symmetric cells in order to determine the anode impedance together with the anode | separator interfacial impedance and (ii) variation in the composite cathode thickness in order to differentiate between the ion transport resistance and the charge transfer resistance of the composite cathode. We show that under the application of stack pressures in the range of 400 MPa, the Li+ exchange current densities can compete with or even exceed those obtained for CAM | liquid electrolyte interfaces.

Heuristic Design of Cathode Hybrid Coating for Power‐Limited Sulfide‐Based All‐Solid‐State Lithium Batteries

AbstractEngineered cathode active materials are critical for the cycling stability and power capability of sulfide‐based all‐solid‐state lithium batteries (ASSBs), yet it is challenging to construct uniform coverage via a scalable approach. In addition, the implication of dielectric coatings for electronic migration blocking in the composite cathode is neglected habitually. A heuristic “polymer‐patched inorganic” cathode coating strategy is presented herein. Single‐crystalline LiNi0.6Co0.2Mn0.2O2 (SNCM) particles are uniformly coated with a hybrid layer comprising nanoscale Li1.4Al0.4Ti1.6(PO4)3 (LATP) and cyclized polyacrylonitrile (cPAN), via a scalable solution‐based method. The LATP coating ensures rapid Li+ transfer across the interface and offers high oxidation tolerance. cPAN partially‐submerges and patches the imperfections of the LATP coating layer, producing a high‐quality protective coating without compromising electronic transfer. Accordingly, sulfide‐based ASSBs employing the hybrid‐modified SNCM cathode demonstrate competitive electrochemical performance in terms of capacity retention (72.7% over 500 cycles, at 0.5 C), and rate capability (87.3 mAh g−1 at 2 C, 5 times that of the pristine SNCM). Significant improvements are attributed to the homogeneity and functionality of the coating, which mitigates parasitic reactions at the interface while simultaneously preserving indispensable electronic percolation. This work offers a brand‐new cathode coating protocol for sulfide‐based all‐solid‐state to achieve longevity and good power.

Simultaneous Li2MoO4 coating and Mo6+ doping improves the structural stability and electrochemical properties of nickel-rich LiNi0.83Co0.11Mn0.06O2

High-nickel ternary material LiNixCoyMn1-x-yO2 (NCM) as a cathode material of Li-ion batteries has already been applied in many fields, like electric vehicles and 3C, due to its low cost and outstanding energy storage performance. but fast capacity decays result from interfacial degradation and internal destruction of the NCM structure leading to poor cycle life during charge–discharge processes, hindering widespread application. To solve these problems, this work develops a modification scheme to achieve the one-step generation of a Li2MoO4 coating on the outside of LiNi0.83Co0.11Mn0.06O2 particles and dope high-valence cations (Mo6+) inside LiNi0.83Co0.11Mn0.06O2 while reducing the residual Li content on the outside of materials. At 1C(1C = 200mAhg−1), the modified sample, Mo + NCM-1.0 (1.0 mol% doped LiNi0.83Co0.11Mn0.06O2), exhibits an excellent discharge capacity of 202mAhg−1 and cycling stability with a capacity retention of 90.22%. By contrast, pristine LiNi0.83Co0.11Mn0.06O2 shows the discharge capacity is 189.27mAhg−1 with a capacity retention of 87.93%. Further research shows that the modification scheme can alleviate the electrode loss during cycling, stabilize the internal structure of the NCM, enhance the Li+ diffusion rate, and improve the electrochemical properties. This modification strategy can be applied to other cathode materials.

One-Pot Synthesis of LiAlO2-Coated LiNi0.6Mn0.2Co0.2O2 Cathode Material

The chemistry of lithium-ion batteries (LIBs) is an active area of research, notably through the increasing demand for high energy and power density in LIBs, especially for application in electric vehicles (EVs) and hybrid electric vehicles (HEVs).Among the various cathode materials, LiNixCoyMn1-x-yO2 (NMC) intercalation compounds are the best candidates for applications in high performance LIBs. However, Ni-rich NMC suffers mainly from parasitic side reactions at the interface with the electrolyte, which leads to a lower thermal and electrochemical stability. Surface modification via coating is an effective concept to counter the capacity degradation of NMC and to improve the particles’ structural stability for enhancing their cycle-life [1], [2]. Different processing techniques that usually requires several steps are presented in the literature. However, to facilitate the integration of a new product in the current battery market, it is preferable to reduce the number of steps during the synthesis process. In this work, we propose a one-pot synthesis of LiAlO2-coated LiNi0.6Mn0.2Co0.2O2 particles, by using a continuous stirred-tank reactor (CSTR).Firstly, the composition and morphology of the coated and uncoated cathode materials are characterized by SEM, TEM, EDX and XPS. Then, the structural characterization of our materials is validated by XRD analysis. Consequently, we will compare the electrochemical performance and thermal stability of coated and uncoated NMC particles.We will demonstrate that our approach provides an easy way to apply surface treatment onto Ni-rich NMC particles and simplifies the synthesis process at large scale production.KEYWORDS: Lithium-ion battery, Ni-rich NMC cathode, LiAlO2 coating, surface protection. Negi, R.S., et al., Enhancing the Electrochemical Performance of LiNi0.70Co0.15Mn0.15O2 Cathodes Using a Practical Solution-Based Al2O3 Coating. ACS Applied Materials & Interfaces, 2020. 12(28): p. 31392-31400.Kim, H.-S., et al., Enhanced electrochemical properties of LiNi1/3Co1/3Mn1/3O2 cathode material by coating with LiAlO2 nanoparticles. Journal of Power Sources, 2006. 161(1): p. 623-627.

Understanding the Stability of LiNi0.5Mn0.5O2 as a Co-Free Positive Electrode.

To understand the stability of Co-free positive electrode materials, LiNi0.5Mn0.5O2 was synthesized with different amounts of lithium added during calcination. The valence states of the Ni and Mn transition metals of the prepared samples were determined through accurate stoichiometry analyses (via inductively coupled plasma optical emission spectrometry), magnetic moment measurements (via superconducting quantum interference device magnetometry), and element valence analyses (via X-ray spectroscopy in combination with Ar ion etching for depth profiling). Unexpectedly, the Ni and Mn transition metals in the interior and on the surface of the LiNi0.5Mn0.5O2 particles show different electrochemical properties. This clarifies the open questions on the Li deintercalation mechanism in LiNi0.5Mn0.5O2.

Surface Functionalization of LiNi7.0Co0.15Mn0.15O2 with Fumed Li2ZrO3 via a Cost‐Effective Dry‐Coating Process for Enhanced Performance in Solid‐State Batteries

AbstractApplying a thin film coating is a vital strategy to enhance long term and interface stability of Ni‐rich layered oxide cathode materials (NRLOs), especially when they are matched with sulfidic solid electrolytes (SSEs) in solid‐state batteries (SSBs). The coating prevents direct contact between the cathode active material (CAM) and the SSE, shielding against parasitic side reactions at the cathode electrolyte interface (CEI). Conventional coatings are based on wet‐chemical methods and therefore harmful to the environment and require long‐lasting processing and high costs. In this study, we present a versatile, facile and highly‐scalable dry‐coating method (with suitable equipment up to 500 kg per batch) successfully employed for both multi‐ and single‐crystalline LiNi0.70Mn0.15Co0.15O2 (NCM70) particles by fumed Li2ZrO3 nanostructured particles (LZONPs) via high intensity mixing process. The resulting porous coating layer stays firmly attached at the CAM particle surface without a need of post‐calcination step at elevated temperatures. The electrochemical testing results signify enhanced rate capability up to 1.5 mA cm−2 for both particle types and cyclic stability up to 650 cycles with a capacity retention of 86.1 % for single‐crystalline NCM70. We attribute the enhanced performance to the reduced CEI reactions as cathodic charge transfer resistance depressed significantly after dry‐coating by LZONPs, being an important step towards sulfidic solid‐state batteries.

In Situ Formation of Lithium Polyacrylate Binder for Aqueous Manufacturing and Recycling of Ni-Rich Cathodes

Water has now become the standard process solvent for graphite-based anodes, eliminating the use of toxic and costly N-Methyl-pyrrolidone (NMP) in anode manufacturing. Ideally, water could also become the standard for cathodes; however, water-based processing of NMC cathode materials induces lithium leaching, which reduces their specific capacity and leads to capacity fade. Here, we demonstrate that leached lithium ions can be exploited during aqueous slurry preparation to create a Li-containing polymer binder that enables cathode performance comparable to those fabricated using NMP. Specifically, we show that leached lithium ions from LiNi0.8Mn0.1Co0.1O2 (NMC 811) particles react with polyacrylic acid (PAA) to form a lithium polyacrylate (LPA) surface coating and binder. Because the resulting LPA binder is water soluble, aqueous-based recycling of the cathode particles is feasible and over 90% capacity retention is shown in recycled material after 100 cycles.

CNT-Strung LiMn2 O4 for Lithium Extraction with High Selectivity and Stability.

LiMn2 O4 is of great potential for selectively extracting Li+ from brines and seawater, yet its application is hindered by its poor cycle stability and conductivity. Herein a two-step strategy to fabricate highly conductive and stable CNT-strung LiMn2 O4 (CNT-s-LMO) is reported, by first stringing Mn3 O4 particles with multiwalled carbon nanotube (CNT), then converting the hybrids into CNT-s-LMO through hydrothermal lithiation. The as-synthesized CNT-s-LMO materials have a net-like structure with CNTs threading through LMO particles. This unique structure has endowed the CNT-s-LMO electrode with excellent conductivity, high specific capacitance, and enhanced rate performance. Because of this, the CNT-s-LMO electrode in the hybrid capacitive deionization cell (HCDI) can deliver a high Li+ extraction percentage (≈84%) in brine and an outstanding lithium selectivity with a separation factor of ≈181 at the Mg2+ /Li+ molar ratio of 60. Significantly, the CNT-s-LMO-based HCDI cell has a high stability, evidenced by 90% capacity retention and negligible Mn loss in 100 cycles. This method has paved a new way to fabricate carbon-enabled LMO-based absorbents with tuned structure and superior capacity for electrochemical lithium extraction with high Li+ selectivity and exceptional cycling stability, which may help to tackle the shortage in supply of Li-ion batteries in industry in the future.

MOF-Derived Long Spindle-like Carbon-Coated Ternary Transition-Metal-Oxide Composite for Lithium Storage.

Fe3O4 is a promising alternative for next-generation lithium-ion batteries (LIBs). However, its poor cycle stability due to the large volume effect during cycling and poor conductivity hinders its application. Herein, we have successfully designed and prepared a carbon-coated ternary transition-metal-oxide composite (noted as (FeCoNi)3O4@C), which is derived from FeCoNi-MOF-74 (denoted as FeCoNi-211-24). (FeCoNi)3O4@C perfectly inherited the long spindle-shaped precursor structure, and (FeCoNi)3O4 particles grew in situ on the precursor surface. The ordered particles and the carbon-coated structure inhibited the agglomeration of particles, improving the material’s cycle stability and conductivity. Therefore, the electrode exhibited excellent electrochemical performance. Specifically, (FeCoNi)3O4@C-700 presented excellent initial discharge capacity (763.1 mAh g–1 at 0.2 A g–1), high initial coulombic efficiency (73.8%), excellent rate capability, and cycle stability (634.6 mAh g–1 at 0.5 A g–1 after 505 cycles). This study provides a novel idea for developing anode materials for LIBs.

Molecular‐Scale Hydrophobic Modification of Ni‐Rich Cathode Materials Toward Superior Critical Endurability and Environmental Stability

AbstractNi‐rich layered oxides have been considered one of the most promising cathode materials for lithium‐ion batteries on account of their high reversible capacity. However, their chemical sensitivity to moisture and carbon dioxide results in the formation and growth of residual lithium compounds, leading to a deterioration in electrochemical performance and difficulty in cathode electrode preparation. In this work, a passivation coating of polydimethylsiloxane with 5 molecular layers is successfully coated on LiNi0.8Co0.1Mn0.1O2 particles. To examine the hydrophobicity of polydimethylsiloxane, bare and coated NCM811 are exposed to a hot and humid chamber for dozens of hours, even exposure to damp air over 120 h. The results indicate that the hydrophobic coating can inhibit the formation and growth of residual lithium compounds on the surface of LiNi0.8Co0.1Mn0.1O2, resulting in slightly less degradation in electrochemical performance. Herein, a rapid, low‐cost, and easily employed method to generate an even hydrophobic/passivation surface is developed, which provides a generic approach to treat various electrode materials, especially nanosized and water‐sensitive ones, to improve their tolerance to extreme environments.

Multi-scale boron penetration toward stabilizing nickel-rich cathode

Nickel-rich layered oxides LiNixCoyMn1-x-yO2 (x ≥ 0.8) have been recognized as the preferred cathode materials to develop lithium-ion batteries with high energy density (>300 Wh kg−1). However, the poor cycling stability and rate capability stemming from intergranular cracks and sluggish kinetics hinder their commercialization. To address such issues, a multi-scale boron penetration strategy is designed and applied on the polycrystalline LiNi0.83Co0.11Mn0.06O2 particles that are pre-treated with pore construction. The lithium-ion conductive lithium borate in grain gaps functions as the grain binder that can bear the strain/stress from anisotropic contraction/expansion, and provides more pathways for lithium-ion diffusion. As a result, the intergranular cracks are ameliorated and the lithium-ion diffusion kinetics is improved. Moreover, the coating layer separates the sensitive cathode surface and electrolyte, helping to suppress the parasitic reactions and related gas evolution. In addition, the enhanced structural stability is acquired by strong B-O bonds with trace boron doping. As a result, the boron-modified sample with an optimized boron content of 0.5% (B5-NCM) exhibits a higher initial discharge capacity of 205.5 mAh g−1 at 0.1C (1C = 200 mA g−1) and improved capacity retention of 81.7% after 100 cycles at 1C. Furthermore, the rate performance is distinctly enhanced by high lithium-ion conductive LBO (175.6 mAh g−1 for B5-NCM and 154.6 mAh g−1 for B0-NCM at 5C).

Thermally sprayed MCO/FeCr24 interconnector with improved stability for tubular segmented-in-series SOFCs

The present work aims to evaluate the feasibility of thermally sprayed Mn1.5Co1.5O4/FeCr24 interconnect under real operating environment of tubular solid oxide fuel cells (SOFC). Different from the planar SOFC, further practical application of ferritic stainless steels interconnector is still limited in tubular SOFC, mainly due to the special construction and complex operating environment. Investigating the stability of interconnector under reducing-oxidizing (redox) atmosphere is an important issue towards practical applications of tubular SOFC. In this work, thermal spraying was applied as a cost-effective method to prepare the segmented-in-series SOFCs based on Mn1.5Co1.5O4/FeCr24 interconnector. The detailed heating and deposition process for different Mn1.5Co1.5O4 particles, quantitative relationship between the Mn1.5Co1.5O4 coating thickness (δ0) and microstructure homogenization rate (dδ/dt) during oxidizing treatment, as well as the feasibility of thermally-sprayed Mn1.5Co1.5O4/FeCr24 interconnect for tubular SOFC applications in range of 600–800 °C were thoroughly evaluated.

A two-phase ultrafine-grained NbMoTaWV refractory high entropy alloy with prominent compressive properties

A NbMoTaWV high entropy alloy (HEA) was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Characterization of milled powders indicated that only a single body-centered cubic (BCC) solid solution phase was generated in the MA process. After SPS, a tetragonal (Ta,V)O2 oxide phase precipitated from the primary BCC phase. The NbMoTaWV alloy exhibited a compressive yielding strength (σy) of 2785 MPa, compressive strength (σmax) of 3661 MPa and strain to failure (εf) of 16.2% at room temperature. The compressive yielding strength of the sintered alloy was dramatically higher compared with most previously reported HEAs. The compressive strength of NbMoTaWV alloy at 1000 °C arrived at 1978 MPa. The excellent strength at room and elevated temperatures are mostly ascribed to the fine (Ta,V)O2 particles dispersed in the BCC matrix.