Particle Surface Research Articles

Structure and particle surface analysis of Li2S–P2S5–LiI-type solid electrolytes synthesized by liquid-phase shaking

AbstractLi2S–P2S5–LiI-type solid electrolytes, such as Li4PS4I, Li7P2S8I, and Li10P3S12I, are promising candidates for anode layers in all-solid-state batteries because of their high ionic conductivity and stability toward Li anodes. However, few studies have been conducted on their detailed local structure and particle surface state. In this study, Li7P2S8I (Li2S: P2S5:LiI = 3:1:1) solid electrolytes as the chemical composition were synthesized by mechanical milling and liquid-phase shaking, and their local structures were analyzed by transmission electron microscopy. The particle surface states were analyzed by X-ray photoelectron spectroscopy, high-energy X-ray scattering measurements, and neutron total scattering experiments. The results showed that Li7P2S8I solid electrolytes are composed of nanocrystals, such as Li4PS4I, LiI, Li10P3S12I and an amorphous area as the main region, indicating that the crystalline components alone do not form ionic conductive pathways, with both the amorphous and crystalline regions contributing to the high ionic conductivity. Moreover, the ionic conductivity of the crystalline/amorphous interface of the glass-ceramic was higher than that of the Li2S–P2S5–LiI glass. Finally, an organic-solvent-derived stable surface layer, which was detected in the liquid-phase shaking sample, served as one of the factors that contributed to its high stability (which surpassed that of the mechanically milled sample) toward lithium anodes. We expect these findings to enable the effective harnessing of particle surface states to develop enhanced sulfide solid electrolytes.

Effect of Particle Size on Optical and Electrical Properties of Thin Films – A Simulation Approach

Abstract This work presents a simulated investigation of the relationship between surface roughness and particle size as well as the resulting impact on the thin film's physical, optical, and electrical properties. Non-porous thin films are created through computer simulation for a range of particle sizes. Random deposition with a surface relaxation technique is used for the generation of non-porous thin films. The fundamental data of two well-known materials, ZnO and CdSe, were used for the theoretical calculation of different parameters like bandgap, absorption coefficient, refractive index, dielectric constant conductivity, or others. It is also shown that the pre-assumed values of all these parameters are well matched with the experimental results reported by different groups. This is probably the first effort to develop a direct relation between the particle size with different fundamental optical or electrical properties of different materials. This would definitely help the experimental researchers in the field of material science to design their experiments as per the desired requirements.


Open Cross-gap Gold Nanocubes with Strong, Large-Area, Symmetric Electromagnetic Field Enhancement for On-Particle Molecular-Fingerprint Raman Bioassays.

Plasmonic nanoparticles with an externally open nanogap can localize the electromagnetic (EM) field inside the gap and directly detect the target via the open nanogap with surface-enhanced Raman scattering (SERS). It would be beneficial to design and synthesize the open gap nanoprobes in a high yield for obtaining uniform and quantitative signals from randomly oriented nanoparticles and utilizing these particles for direct SERS analysis. Here, we report a facile strategy to synthesize open cross-gap (X-gap) nanocubes (OXNCs) with size- and EM field-tunable gaps in a high yield. The site-specific growth of Au budding structures at the corners of the AuNC using the principle that the Au deposition rate is faster than the surface diffusion rate of the adatoms allows for a uniform X-gap formation. The average SERS enhancement factor (EF) for the OXNCs with 2.6 nm X-gaps was 1.2 × 109, and the EFs were narrowly distributed within 1 order of magnitude for ∼93% of the measured OXNCs. OXNCs consistently displayed strong EM field enhancement on large particle surfaces for widely varying incident light polarization directions, and this can be attributed to the symmetric X-gap geometry and the availability of these gaps on all 6 faces of a cube. Finally, the OXNC probes with varying X-gap sizes have been utilized in directly detecting biomolecules with varying sizes without Raman dyes. The concept, synthetic method, and biosensing results shown here with OXNCs pave the way for designing, synthesizing, and utilizing plasmonic nanoparticles for selective, quantitative molecular-fingerprint Raman sensing and imaging applications.

Study on the effects of inorganic salts and ionic surfactants on the wettability of coal based on the experimental and molecular dynamics investigations

Through the evaluation and preparation of a novel inorganic salt composite solution consisting of sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactants polyethylene glycol pisooctyl phenyl ether (Triton X-100), and inorganic salt Na2SO4, based on surface tension, contact angle, settling time, wetting rate, and changes in the surface microstructure and functional groups of coal, this study analyzed the wetting behavior of the solution on coal dust and its adsorption capacity on the surface of coal particles. The results demonstrate that the composite solution of inorganic salts can significantly enhance the wettability of coal samples, reducing the contact angle to 21.54° and lowering the surface tension to 26.10 mN/m. After treatment with the solution, the relative content of oxygen-containing functional groups in the microscopic structure of the coal sample increased to 59.6 % and pores more prominent than 25 nm increased to 34.63 %. Molecular dynamics (MD) simulations of the water-inorganic salt composite solution-coal system are conducted using Materials Studio software, revealing that after the addition of the composite solution, the self-diffusion coefficient (D) of water molecules is 6.3 × 10-9 m2/s, the starting point of the composite solution is 15 Å, and the system's interaction energy increase to 14000 kcal/mol. It further elucidated the modification of the surface molecular structure of coal dust by the inorganic salt composite solution, increasing hydrogen bonds, enhancing wetting, and demonstrating a solid adsorption capability of the inorganic salt composite solution on the surface of coal dust.

Sphaerothrix gracilis gen. et sp. nov. (Nodosilineales, Cyanobacteria): a novel filamentous cyanobacterium isolated from tropical coastal microplastics

SUMMARYCyanobacteria are ancient organisms that contribute significantly to primary production in aquatic ecosystems. Although they are a group of microbes present in a wide range of environments, their diversity on anthropogenic substrates, namely microplastics, is still largely unknown. In the present study, we describe a new genus and species of cyanobacteria from the Nodosilineaceae family. Strains were isolated from foam microplastic particles obtained from beach sediments facing the Singapore Strait. This species is morphologically similar to the polyphyletic, cosmopolitan Leptolyngbya spp.; however, it forms an independent clade with 16S rRNA phylogeny and has a unique 16S–23S internal transcribed spacer secondary structure. To date, no cyanobacteria have been isolated and cultured from the surfaces of microplastic particles. Using a polyphasic approach combining morphological, phylogenetic and ecological traits, we describe a new genus and species Sphaerothrix gracilis. The presence of certain cyanobacteria rafting on microplastic surfaces can potentially indicate a long‐distance transport into new ecosystems with implications on toxicity and biodiversity.

Preparation of high-concentration coal-water slurry based on the bearing model method of spherical particles

ABSTRACT Coal-water slurry (CWS), a mixture of pulverized coal, water, and additives, is a clean liquid coal-based fuel for gasification. Superhydrophobic surface modification using a secondary particle-second liquid system is an effective CWS preparation method. In this study, the effect of the sphericity of the secondary particles on the rheological properties of CWS samples was investigated. Spherical secondary particles were found to roll in the film layer of the second liquid, resulting in a lower apparent viscosity of the CWS. The bearing model refers to the spherical secondary particle on the surface of the coal particle, similar to the balls in a bearing, which can transform sliding friction into rolling friction. The bearing model can effectively reduce frictional resistance. By modifying the coal particles with the suspension of secondary particles in the second liquid, a 73% CWS sample with good fluidity was prepared. The apparent viscosity of the 73% CWS prepared without any modification of the coal particles was 13,329.2 mPa·s, and the flow grade was C. The apparent viscosity of the 73% CWS prepared using coal particles modified with the spherical glass bead suspension was 2102.8 mPa·s, and its flow grade was A.

Mineralogical approach on laboratory weathering of uncontaminated Ryugu particles: Comparison with Orgueil and perspective for storage and analysis

AbstractAlthough CI chondrites are susceptible to terrestrial weathering on Earth, the specific processes are unknown. To elucidate the weathering mechanism, we conduct a laboratory experiment using pristine particles from asteroid Ryugu. Air‐exposed particles predominantly develop small‐sized euhedral Ca‐S‐rich grains (0.5–1 μm) on the particle surface and along open cracks. Both transmission electron microscopy and synchrotron‐based computed tomography combined with XRD reveal that the grains are hydrous Ca‐sulfate. Notably, this phase does not form in vacuum‐ or nitrogen‐stored particles, suggesting this result is due to laboratory weathering. We also compare the Orgueil CI chondrite with the altered Ryugu particles. Due to the weathering of pyrrhotite and dolomite, Orgueil contains a significant amount of gypsum and ferrihydrite. We suggest that mineralogical changes due to terrestrial weathering of particles returned directly from asteroid occur even after a short‐time air exposure. Consequently, conducting prompt analyses and ensuring proper storage conditions are crucial, especially to preserve the primordial features of organics and volatiles.

Manipulating Local Chemistry and Coherent Structures for High-Rate and Long-Life Sodium-Ion Battery Cathodes.

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na+ transport kinetics, elucidated by density functional theory calculations. Elevated Jahn-Teller [Mn3+O6] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na+ diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g-1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

Self-diffusiophoretic propulsion of a spheroidal particle in a shear-thinning fluid

Shear-thinning viscosity is a non-Newtonian behaviour that active particles often encounter in biological fluids such as blood and mucus. The fundamental question of how this ubiquitous non-Newtonian rheology affects the propulsion of active particles has attracted substantial interest. In particular, spherical Janus particles driven by self-diffusiophoresis, a major physico-chemical propulsion mechanism of synthetic active particles, were shown to always swim slower in a shear-thinning fluid than in a Newtonian fluid. In this work, we move beyond the spherical limit to examine the effect of particle eccentricity on self-diffusiophoretic propulsion in a shear-thinning fluid. We use a combination of asymptotic analysis and numerical simulations to show that shear-thinning rheology can enhance self-diffusiophoretic propulsion of a spheroidal particle, in stark contrast to previous findings for the spherical case. A systematic characterization of the dependence of the propulsion speed on the particle's active surface coverage has also uncovered an intriguing feature associated with the propulsion speeds of a pair of complementarily coated particles not previously reported. Symmetry arguments are presented to elucidate how this new feature emerges as a combined effect of anisotropy of the spheroidal geometry and nonlinearity in fluid rheology.

Comparison of Newtonian and glycerol-water solution-based SiO2 nanofluid droplets impacting on heated spherical surfaces

The dynamic interactions of liquid droplets with heated spherical particles, relevant across various scientific and engineering disciplines, display intriguing collision behaviors whose principles are yet to be fully deciphered. This investigation utilizes high-speed photography to explore the wetting and non-wetting responses of different Newtonian and glycerol-water solution-based SiO2 nanofluid droplets upon contact with heated particles. Findings indicate that nanofluid droplets disrupt the thermal field and modify the surface morphology of particles more extensively under wetting than non-wetting conditions. Wetting conditions lead to significant alterations in the liquid film thickness and notable velocity field disruptions for droplets of deionized water and glycerol solution. Conversely, in the non-wetting phase, droplets nearing full rebound cause less disturbance to the velocity field, a behavior consistent across all fluid types and particle temperatures. The shape changes nanofluid droplets undergo when rebounding and separating from the particle surface are similar to those seen in glycerol solution and water droplets. Droplets in the breakup-rebound phase experience shorter contact times than those merely rebounding. A phase diagram is presented, detailing wetting (receding-deposition and boiling-breakup) and non-wetting (rebound and breakup-rebound) actions. An increase in the Weber number necessitates a higher particle temperature for the transition from rebound to breakup-rebound, which corroborates with theoretical insights. Furthermore, droplets achieve their maximum spreading area during the boiling-breakup mode.

Polybutylene adipate terephthalate (PBAT) composites for thermally conductive, fire retardant, high dielectric applications using BaTiO3 and MWCNTs as fillers

This study provides a comprehensive investigation of the fabrication of novel composite materials by blending polybutylene adipate terephthalate (PBAT) with barium titanate (BaTiO3) and multiwalled carbon nanotube (MWCNT) fillers. Prior to fabricating the composites, the filler surface treatments were tailored to enhance their compatibility with the PBAT matrix. Adipic acid (AA), a monomer for PBAT, was employed on the surface of the BaTiO3 particles, while butanediol (BD) also a monomer of PBAT was used to modify the surface of the MWCNTs to ensure effective interaction with the PBAT chains during the composite fabrication process. The composite samples were produced by melt-blending at 140 °C, followed by injection molding at the same operating temperature for subsequent analysis. The results revealed remarkable improvements in the dielectric constant, thermal conductivity, fire retardancy, and tensile strength of the 40 wt% BaTiO3 and MWCNT-PBAT blends compared to pure PBAT. The incorporation of BaTiO3 additionally contributed to enhanced fire retardancy, mechanical properties, and dielectric properties, making the composite material more resistant to ignition and flame spread, thus rendering it suitable for applications requiring elevated fire safety. In addition, the inclusion of MWCNT improved thermal conductivity, enabling promising and efficient heat dissipation in various applications.

Environmentally Friendly Synthesis of Polymer Nanoparticles in a Packed Reactor Using Glass Beads

AbstractPolymeric particles less than 100 nm in size (polymer nanoparticles), which are useful in the fields of medicine and so on, are synthesized through emulsion polymerization, wherein surfactants are essential for maintaining their dispersion stability, contaminating particle surfaces and causing high environmental pollution. The soap‐free emulsion polymerization (SFEP) of styrene in a packed reactor using microglass beads enables the synthesis of polymer nanoparticles without surfactants. Ultraviolet irradiation is used for radical polymerization using an initiator during the SFEP of styrene. The reaction space in the packed reactor is controlled by the size of glass beads to be filled in the reactor. A decrease in the size of the glass beads narrows the reaction space, causing the average polystyrene particle size to reach 27.3 nm and suppress convection flow by the wall of the glass beads, thereby limiting particle motion and preventing particle growth through particle collisions.This article is protected by copyright. All rights reserved

Innovative production of phosphoric acid-hydrolyzed chitin nanocrystals for Pickering emulsion stabilization

Addressing the need for sustainable emulsification methods, this study introduces a novel approach by producing chitin nanocrystals (PA-ChNCs) through solid-state hydrolysis using minimal phosphoric acid. The aim was to assess the capability of PA-ChNCs to stabilize Pickering emulsions. Our investigation revealed a pH-responsive variation in particle size and surface charge of PA-ChNCs, critical for emulsion stability. They varied from 321.5 ± 10.5 nm to 2366.7 ± 171.6 nm and from 33.7 ± 1.2 mV to −19.9 ± 1.4 mV, respectively, when pH increased from 3 to 10. Notable, emulsions with a 50% oil-to-water (O:W) ratio presented larger droplets with increased viscosity, enhancing stability over 30 days significantly. In contrast, higher PA-ChNCs concentrations (2.0 wt%) at pH 10 resulted in smaller droplets and higher viscosity, indicating superior emulsion stability. This research contributes novel insights into eco-friendly emulsifier development, utilizing seafood byproducts and underscoring the use of PA-ChNCs as effective Pickering emulsion stabilizers in food applications.

Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry.

Uranyl fluoride (UO2F2) particles (<20 μm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO2F2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC-ICP-MS for high precision isotopic (i.e., 234U, 235U, and 238U) analysis. This method, LIBS/LA-MC-ICP-MS was optimized and employed to rapidly measure 80+ UO2F2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235U/238U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234U/238U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here.

Usefulness of percutaneous estradiol-loaded PLGA-PEG-PLGA nanoparticles for the treatment of osteoporosis

Compared with poly (dl-lactide-co-glycolide) (PLGA) nanoparticles, triblock copolymer (PLGA-PEG-PLGA) nanoparticles composed of PLGA and polyethylene glycol (PEG) may improve the skin permeability of drugs. In this study, the usefulness of estradiol-loaded (E2-loaded) PLGA-PEG-PLGA nanoparticles in the treatment of osteoporosis was investigated by comparison with E2-loaded PLGA nanoparticles. The cumulative E2 permeation of each nanoparticle through rat skin was quantified using a Franz cell. The results showed that PLGA-PEG-PLGA nanoparticles had significantly higher permeation than PLGA nanoparticles. Next, in vivo treatment experiments were conducted using an ovariectomized rat model of osteoporosis. Nanoparticles were administered once per week in combination with iontophoresis. At 6 weeks after the initiation of treatment, significant improvement in bone density was observed in the treated group compared with the untreated group. The improvement in bone density tended to be greater in the PLGA-PEG-PLGA nanoparticle group versus the PLGA nanoparticle group. This may be attributed to the higher hydrophilicity of the particle surface of PLGA-PEG-PLGA nanoparticles compared with PLGA nanoparticles and the improved skin permeability of the particles through the trans-adnexal pathway.

Simple two-step synthesis of Ag/ZnO nanoparticles with enhanced photocatalytic response

Abstract This study presents a simple two-step synthesis method for the fabrication of Ag/ZnO nanocomposites to improve the photocatalytic response of ZnO. The synthesis involves ZnO nanoparticles that were fabricated from the thermal decomposition of commercial zinc acetate. In order to produce Ag/ZnO nanoparticles in a simple two-step process, ZnO nanoparticles were mixed with Ag nanoparticle suspensions previously obtained by the laser ablation of solids in liquids technique at three different fluences. Structural characterization of ZnO powders revealed the presence of single phase wurtzite ZnO nanoparticles with crystal sizes of 20 nm. On the other hand, XRD patterns for a composite sample revealed the presence of signals associated to both ZnO and Ag suggesting that silver nanoparticles were attached to the ZnO particles surface. &amp;#xD;Optical characterization of the ZnO powders, carried out by UV-Vis spectroscopy, showed a strong absorption band centered at 380 nm, which is associated to excitonic transitions in ZnO nanoparticles, whilst absorption measurements of silver nanoparticles colloids revealed the presence of a strong band centered near 412 nm. This band shifts to shorter wavelengths with increasing fluence from 2.6 to 6.2 J/cm2, indicating changes in nanoparticles size. Photocatalytic degradation tests of methylene blue under UV irradiation were carried out using pure ZnO, Ag colloids and Ag/ZnO nanoparticles. After the first 30 minutes of irradiation, it was observed that the silver nanoparticles reached degradation percentages of 16, 22 and 29 % for samples synthesized at 2.6, 4.2 and 6.2 J/cm2, respectively. Meanwhile the ZnO sample reached a value of 13 % after 30 minutes. Regarding the Ag/ZnO composite sample, the percentage of degradation after 30 minutes was 36%, demonstrating a considerable enhanced photocatalytic activity as compared to ZnO. After 24h irradiation, Ag/ZnO degraded 95% of the methylene blue solution. It was observed that decorating ZnO with laser produced silver nanoparticles accelerates the photocatalytic response of ZnO by enhancing the activity at short times. &amp;#xD;

From creep to flow: Granular materials under cyclic shear

When unperturbed, granular materials form stable structures that resemble the ones of other amorphous solids like metallic or colloidal glasses. Whether or not granular materials under shear have an elastic response is not known, and also the influence of particle surface roughness on the yielding transition has so far remained elusive. Here we use X-ray tomography to determine the three-dimensional microscopic dynamics of two granular systems that have different roughness and that are driven by cyclic shear. Both systems, and for all shear amplitudes Γ considered, show a cross-over from creep to diffusive dynamics, indicating that rough granular materials have no elastic response and always yield, in stark contrast to simple glasses. For the system with small roughness, we observe a clear dynamic change at Γ ≈ 0.1, accompanied by a pronounced slowing down and dynamical heterogeneity. For the large roughness system, the dynamics evolves instead continuously as a function of Γ. We rationalize this roughness dependence using the potential energy landscape of the systems: The roughness induces to this landscape a micro-corrugation with a new length scale, whose ratio over the particle size is the relevant parameter. Our results reveal the unexpected richness in relaxation mechanisms for real granular materials.

Nano-ZnO modified hydroxyapatite whiskers with enhanced osteoinductivity for bone defect repair

Abstract Hydroxyapatite (HA) whisker (HAw) represents a distinct form of HA characterized by its high aspect ratio, offering significant potential for enhancing the mechanical properties of bone tissue engineering scaffolds. However, the limited osteoinductivity of HAw hampers its widespread application. In this investigation, we observed HAw punctured osteoblast membranes and infiltrated the cell body, resulting in mechanical damage to cells that adversely impacted osteoblast proliferation and differentiation. To address this challenge, we developed nano-zinc oxide particle-modified HAw (nano-ZnO/HAw). Acting as a reinforcing and toughening agent, nano-ZnO/HAw augmented the compressive strength and ductility of the matrix materials. At the same time, the surface modification with nano-ZnO particles improved osteoblast differentiation by reducing the mechanical damage from HAw to cells and releasing zinc ion, the two aspects collectively promoted the osteoinductivity of HAw. Encouragingly, the osteoinductive potential of 5%nano-ZnO/HAw and 10%nano-ZnO/HAw was validated in relevant rat models, demonstrating the efficacy of this approach in promoting new bone formation in vivo. Our findings underscore the role of nano-ZnO particle surface modification in enhancing the osteoinductivity of HAw from a physical standpoint, offering valuable insights into the development of bone substitutes with favorable osteoinductive properties while simultaneously bolstering matrix material strength and toughness.

Densification and shaping of pure Cu-BTC powders using a solid-state chemical transformation.

Abstract MOFs are a class of porous crystalline materials whose unique properties have led to applicability in several fields ranging from gas adsorption to drug delivery. Despite their high potential, MOFs are usually found as fine powders, a property that can limit their use in &amp;#xD;industrial applications. Here, a novel approach is proposed to form densified Cu-MOF (Cu BTC) powders and monoliths using 1,2-ethanedisulfonic acid (EDSA) as a densification agent. A MOF/EDSA mixture was heated to ~150°C; the molten EDSA not only promotes the growth of larger MOF crystallites, but also stimulates condensation reactions between the carboxylate-based MOF ligands, further binding the particles together. When this reaction was done in a stainless-steel die under pressure MOF-based monoliths could also be formed. Notably, using this approach, the MOF had a higher density, significantly improving the volumetric CO2 adsorption capacity. We believe this contribution provides the basis for future work wherein the intrinsic MOF particle surfaces can be selectively engineered to improve their properties towards shaping for industrial applications.

Effect of Subtle Changes in Ni2+/Ni3+ and Particle Surface Area in LiNi0.5Mn0.5-xCoxO2 (x = 0.1 - 0.3) Cathode Materials for Lithium-Ion Batteries

Abstract In Li[Ni,Mn,Co]O2 (NMC) cathode materials, small changes in transition metal ratio and particle surface area can significantly impact capacity retention. To understand the combined effect of transition metal ratio and the particle surface area, we studied LiNi0.5Mn0.5-xCoxO2 (x = 0.1-0.3) particles with two different morphologies: dense, spherical particles and high-surface area aggregates. All compositions in this series contain the same percentage of Ni but have differing amounts of Ni2+ and Ni3+. While Ni2+ tends to induce anti-site defects predominantly in the bulk, Ni3+ promotes particle surface reconstruction, both of which negatively impact capacity retention. Upon cycling to 4.4 V for 100 cycles, we observe that particles of high surface area with high Ni3+ concentration undergo the most severe capacity degradation. However, high surface area particles with high proportion of anti-site defects undergo sluggish capacity fade. Overall, with 60% of Ni2+ and 40% of Ni3+, spherical NMC 532 particles endure the detrimental effects of anti-site defects and surface reconstruction, but neither too prominently and thus emerges as the best candidate among the studied samples. This study highlights the synergy between transition metal ratio and particle surface area and how it determines the properties of the NMC cathode materials.