Morphology Of Primary Particles Research Articles

Understanding the Role of Solvent on the Growth of Zinc Oxide: Insight from Experiment and Molecular Dynamics Simulations.

The controlled synthesis of nanoparticles with tailored shapes and morphologies has garnered significant attention, driven by the ever-growing demand for advanced materials with defined properties. In nanoparticle formation, various parameters influence the final product, and among these, the solvent plays a pivotal role, as it constitutes the major component of the reaction medium. In this work, the critical role of solvents in controlling the growth of zinc oxide (ZnO) nanoparticles was investigated, with a focus on simple primary alcoholic solvents as the reaction medium. A model reaction based on the direct solvolysis of anhydrous zinc acetylacetonate was employed to probe the influence of different primary alcohols, specifically methanol, ethanol, and their mixture. A substantial difference in the preferential growth direction of the ZnO nanocrystals in methanol and ethanol was observed through XRD and was further proven through TEM. Thereby, in ethanol, a preferential growth in the [001] direction was observed, resulting in short nanorods as primary particles, while this growth was inhibited in methanol, leading to platelet- or sheet-like primary particles. To unravel the underlying mechanisms responsible for the observed solvent-dependent variations, molecular dynamics (MD) simulations were employed using an optimized interface force field to model the ZnO-alcohol interaction. These simulations provide valuable insights into the preferential adsorption of the solvent molecules onto the polar (0001) and (0001̅) and nonpolar (101̅0) ZnO surfaces, shedding light on the fundamental interactions driving the shape control phenomenon. Essentially, the experimental observations on primary particle morphology could be explained well by the adsorption behavior determined by the MD simulations. Furthermore, this report provides an extensive comparison with various similar reaction systems for ZnO synthesis, deriving correlations with the findings from the model system. These insights contribute to a deeper understanding of the intricate interplay between solvent properties and nanoparticle growth, offering a valuable toolkit for designing and optimizing the synthesis of ZnO nanoparticles with specific shapes and functionalities.

Beyond dopant selection: The critical grain size window as a key performance dictator for Co-free, Ni-rich cathode materials

Despite the immense potential of cobalt-free, nickel-rich cathode materials to replace their cobalt-containing counterparts in lithium-ion batteries (LIBs), their widespread adoption remains hindered by performance limitations. While extensive research has explored various doping strategies to address this challenge, the reported benefits vary significantly, suggesting an incomplete understanding of dopant influence and thus hindering the full potential of these additives. Our investigation into the effect of various dopants on Li(Ni0.95Mn0.05)O2 performance yielded a surprising discovery: the LIB performance of transition metal-doped Li(Ni0.95Mn0.05)O2 becomes remarkably consistent across different dopant types, provided the calcination conditions are optimized. Regardless of dopant type, a critical grain size window is identified as a key factor influencing the performance of the doped Li(Ni0.95Mn0.05)O2. Calcination within a specific temperature range is paramount to control this previously overlooked performance determinant, which significantly impacts grain growth, primary particle morphology, and lattice structure. This novel insight allows us to demonstrate that cost-effective dopants such as Ti can achieve performance in stabilizing Li(Ni0.95Mn0.05)O2 comparable to that of more expensive, higher-valence alternatives (e.g., Nb, Ta, W, and Mo). This discovery paves the way for developing practical material design processes that meet the stringent requirements of the LIB industry.

Morphology, aspect ratio, and surface elemental composition of primary aerosol particles at urban region of India.

The PM2.5 and PM10 particles were characterized in terms of morphology (size and shape) and surface elemental composition at two different (traffic and industrial) locations in urban region of India and further linked to different morphological defining parameters. The overall PM2.5 and PM10 showed significant daily variability indicating higher PM10 as compared to PM2.5. PM2.5/PM10 ratio was found to be 0.58 ± 0.10 indicating the abundance of PM2.5. Soot aggregates, aluminosilicates, and brochosomes particles were classified based on morphology, aspect ratio (AR), and surface elemental composition of single particles. The linear regression analysis indicates the significant correlation between area equivalent (Daeq) and feret diameter (Dfd) (R2 0.86-0.98). Higher aspect ratio (1.48 ± 0.87-1.43 ± 0.50) was noted at traffic site as compared to industrial site (1.33 ± 0.58-1.29 ± 0.30), while circularity showed the opposite trend. Fractal dimension (Df) of soot aggregates estimated by the soot parameters method (SPM) were found to be 1.70, 1.72, and 1.88, mainly attributed to vehicular emissions, biomass, and industrial emission/coal burning, respectively. This further inferred that freshly emitted soot particles exhibited lacey in nature with spherical shape (Df 1.70) at traffic site, while at industrial location, they were different with compact shapes (Df 1.88) due to particle aging processes. This study inferred the synoptic changes in mass, chemical characteristics, and morphology of aerosol particles which provide the new insights into individual atmospheric particle and their dynamic nature.

Enabling the Strengthened Structural and Interfacial Stability of High‐Nickel LiNi0.9Co0.05Mn0.05O2 Cathode by a Coating‐Doping‐Microstructure Regulation Three‐In‐One Strategy

AbstractHigh‐nickel layered cathodes exhibit great promise in advancing high‐energy‐density batteries owing to their significant advantages in high energy capacity and low cost, but they suffer severe structural and interfacial deterioration during cycling, resulting in safety risk and reduced cycle life. Herein, drawing inspiration from the low melting point infusion capability of Sb2Se3, a three‐pronged strategy aimed at simultaneously achieving coating on primary and secondary particles surface, Sb doping and elongated and slimed primary particle morphology is proposed and developed to fortify the structural and interfacial stability of high‐nickel LiNi0.9Co0.05Mn0.05O2 (NCM90) cathode. The “melted and infused” Sb2Se3 plays a beneficial role in the defensive effect on primary and secondary particle's surfaces, mitigating the interfacial deterioration. In addition, the enhanced structural stability is achieved by both Sb5+ doping and regulated primary particle morphology, contributing to the alleviated particle breakage and ultimately reinforced cycling stability. Consequently, the Sb2Se3‐NCM90 electrodes significantly improve cycling performance, which maintain higher capacity retentions of 96.6% at 4.3 V after 100 cycles and 80.2% at 1C/5C after 500 cycles. The proposed coating‐doping‐microstructure regulation three‐in‐one strategy for improving the cycling stability of high‐nickel NCM cathodes offers innovative ideas for the design and advancement of high‐energy‐density lithium‐ion batteries.

Antimony Doping Enabled Radially Aligned Microstructure in LiNi0.91Co0.06Al0.03O2 Cathode for High‐Voltage and Low‐Temperature Lithium Battery

AbstractNi‐rich layered oxide cathode material with Ni contents greater than 90% is considered as a highly promising candidate for lithium‐ion batteries (LIBs) owing to its remarkable specific capacity and cost‐efficiency. However, severe capacity degradation caused by the structural collapse and interfacial instability with electrolyte under high voltage greatly hinders the practical application. Here, an antimony (Sb)‐doped LiNi0.91Co0.06Al0.03O2 (Sb‐NCA91) cathode is proposed, where the Sb doping modifies the morphology of primary particles and enables the radially aligned microstructure. This unique microstructure can disperse the anisotropic mechanical stress caused by the H2‐H3 phase transformation, and mitigate the shrinkage and expansion of the primary particles during high‐voltage and low‐temperature cycling, thus inhibiting the formation of microcracks and structural deterioration. Meanwhile, the closely arranged radial spokes allow fast ion transport in the secondary particles and effectively improve the rate performance and low‐temperature performance of the cathodes. As a result, the Sb modified cathode demonstrates superior capacity retention of ≈84% at 1 C after 200 cycles in 2.7–4.5 V at 25 °C, while the pristine NCA91 cathode only retains ≈79%. Additionally, the capacity retention at −20 °C is significantly increased from ≈61% (NCA91) to ≈88% (Sb‐NCA91) after 100 cycles.

Inhibiting phase conversion and improving cyclic stability of Ni-rich layered oxide by high-valence element concentration gradient doping

Nickel (Ni)-rich layered oxide cathodes are believed to be one of the crucial materials for the development of high-energy density power batteries. However, accompanied by the Ni content of layered cathodes increases, it encounters some awkward issues such as sensitivity to moisture, side reactions, and gas production. Herein, by using a high-valency elements Tellurium (Te) doping strategy, we successfully design and fabricate the layered oxide cathode material Li[(Ni0.90Co0.10)0.99Te0.01]O2 (1.0 Te-NC90) with a high capacity of 231.36 mAh g−1 at 0.1C, which has high cycling stability of 95.01 % after 100 cycles at 0.5C, good thermal stability of 205 °C and high Li+ diffusion rate of 8.12 × 10−10 cm2 s−1. It has been found that the (003) interplanar spacing of 1.0 Te-NC90 cathode will increase from 0.472 nm to 0.491 nm due to the concentration gradient Te-doping strategy, which can promote Li+ diffusion. Besides, it can refine the grain structure and transform the primary particles from bulk-grained to rod-grained morphology, and these elongated and closely packed particles radiate from the center to the surface with a spoke-like arrangement, which effectively dissipates lattice strain generated during deeply charging states and suppresses the abrupt lattice transformation associated with the H2 → H3 phase, thereby avoiding the development of microcracks during cycling. In the meantime, robust Te-O bonds can keep the material lattice stable to prevent oxygen loss and TM ion movement. Therefore, this study reveals the significant role of trace Te-doping in enhancing crystal structure and electrochemical stability through microstructural engineering for the control of primary particle morphology.

High Volumetric Energy Density LiFePO4/C Cathode Materials Synthesized by Dodecyl Polyglucoside-Assisted Glucose-Polyethylene Glycol Composite Carbon Source

Abstract High volumetric energy density LiFePO4/C cathode materials were synthesized by wet ball milling, spray drying, and carbothermal reduction method using glucose and polyethylene glycol (PEG) as composite carbon sources and dodecyl polyglucoside (C12APG) as a milling aid. With the introduction of C12APG during the ball milling process, the prepared cathode materials have uniform particle size (100-200 nm in diameter) and regular primary particle morphology. In addition, PEG substitutes part of glucose as a carbon source, resulting in low carbon content and high graphitization of residual carbon after high-temperature calcination. The prepared LiFePO4/C cathode materials have a high powder compaction density (2.68 g cm-3) and excellent electrochemical performance (discharged capacities of 161.2 and 141.7 mAh g-1 at 0.2 C and 5 C, and cycle retention of 98.6% for 100 cycles at 1 C/1 C). This LiFePO4/C composite was assembled into 14500-type cylindrical batteries with a compaction density of 2.62 g cm-3 for the positive electrode. The volumetric energy densities of the positive electrode were 1135.18 Wh L-1 and 918.16 Wh L-1 at 0.2 C and 5 C, respectively.

Influence of Primary Particle Morphology and Hydrophilicity of Carbon Matrix on Electrode Coating Quality and Performance of Practical High‐Energy‐Density Li–S Batteries

AbstractLi–S batteries have attracted attention as the next‐generation secondary batteries. While substantial progress is made in understanding Li–S chemistry at a fundamental level, only a limited number of studies are dedicated to achieving high energy density at the practical pouch cell level. The challenge lies in attaining high‐energy‐density Li–S batteries under harsh conditions, which involve a minimal amount of electrolyte and a relatively high areal S‐loading cathode. This discrepancy creates a substantial gap between fundamental material research and comprehensive cell‐level investigations. In this study, it is investigated how the morphology and properties of two carbon materials, namely Ketjen black (KB) and mesoporous carbon nano‐dendrites (MCND), influence the composite cathode architecture and determine the performance of Li–S batteries. Unlike KB, MCND allows for a higher sulfur‐loading cathode without evident cracks in the composite cathode. This achievement can be attributed to the high porosity, excellent wettability, and high conductivity exhibited during an identical electrode preparation procedure. Furthermore, large‐format Li–S pouch cells incorporating MCND/S cathodes are successfully fabricated. These cells demonstrate an energy density surpassing 250 Wh kg−1 and an initial discharge capacity of 3.7 Ah under challenging conditions (S‐loading > 5 mg cm−2 and E/S < 3.5 µL mg−1).

Effect of Doping Process Route on LiNiO2 Cathode Active Material Properties

One way to obtain higher energy densities in lithium-ion batteries is to increase the nickel content in lithium nickel-cobalt-manganese oxide (NCM) cathode active materials (CAMs), ultimately approaching LiNiO2 (LNO). At the same time, a higher nickel content and specific capacity comes with more severe degradation of the CAM during battery cycling. Doping of the CAM with additional elements is a common approach to increase structural stability. For any CAM, comparisons of different dopants with each other and with undoped references are therefore commonly found in the literature.[1,2] In some cases, the effect of different dopants on the CAM particle morphology is also reported.[3,4] However, the influence of the process route of dopant introduction is rarely discussed. The most common ways are either the co-calcination of dopant source, lithium source and CAM precursor (pCAM), or the co-precipitation of dopant ions during pCAM precipitation. Impregnating the pCAM surface with a suspension of smaller dopant particles or a dopant solution, followed by solvent removal, can provide better dopant distribution in case of low dopant ion mobility or phase separation tendencies during calcination.Building on the previous finding that the primary particle morphology is the determining factor of LNO performance,[5,6] in this work, the primary particle morphology, but also dopant distribution in a series of 0.25 mol% Zr-doped LNO obtained from the three different process routes co-calcination, impregnation and co-precipitation, is investigated. This low dopant concentration is common in commercial CAM, as thus the content of redox-active transition metal content remains high to provide maximal energy density. Zr also tends to phase separate in the form of Li2ZrO3 at high concentrations, which is this way avoided as much as possible, since the chosen concentration is below the solubility limit of Zr in the LNO bulk. In this comparison, it is found that not the dopant itself, but the process route of its introduction affects the primary particle morphology of LNO, likely explained by the initial dopant localization early in the calcination.Differences in electrochemical performance, both in coin cells and long-term cycled pouch cells, as well as in specific capacitance and gas evolution are then also found to be due not to the dopant, as one would initially assume in comparisons of doped and undoped materials, but to the effect of the process route on LNO primary particle morphology.

Morphology evolution and growth mechanism of primary Al3Sc and eutectic Al3Sc in Al–Sc alloys

Al–Sc master alloys are crucial raw materials for the preparation of high-strength and high-toughness Al alloys. The primary particles in these alloys are Al3Sc, which has been proved to have strong grain refining and strengthening effects. The material properties are related to the morphology of the primary particles. However, the mechanism of morphological changes of primary Al3Sc particles at different cooling rates during industrial production is not clear. To address this, we conducted a study where we controlled the solidification cooling medium and obtained the primary Al3Sc particles with different morphologies. Also, the three-dimensional (3D) morphology of the eutectic Al3Sc phase was obtained by holding at eutectic temperature for 72 h. The results indicate that the cooling rates have a strong impact on the morphology of primary Al3Sc particles due to their high anisotropy and constitutional supercooling in the melt. The primary Al3Sc particles have a multilayer structure of "Al3Sc+α-Al + Al3Sc+ … ", which can be explained in terms of solidification sequence. The eutectic Al3Sc phase is fibrous and perpendicular to the surface of the matrix or the primary Al3Sc particle, and grows in a spiral pattern.

Advances of high-performance LiNi1-x-yCoxMyO2 cathode materials and their precursor particles via co-precipitation process

Layered LiNi1-x-yCoxMyO2 (M = Mn or Al) is a promising cathode material for lithium-ion batteries due to its high specific capacity and acceptable manufacturing cost. However, the polycrystalline LiNi1-x-yCoxMyO2 cathode material suffers from disordered orientation of primary particles and poor geometric symmetry of secondary particles, which severely hampers the migration of Li+ ions. Furthermore, the resulting anisotropy accelerates the disintegration of the secondary particle structure, significantly affecting the electrochemical performance of the polycrystalline cathode. In spite of less grain boundary, the single-crystal LiNi1-x-yCoxMyO2 cathodes still suffer from severe microcracks generated by repeated planar gliding during cycling, which poses a great challenge to the cycling stability of single-crystal materials. It's worth noting that the microstructure of the cathode material is mainly inherited from its precursor. Therefore, it is necessary to deeply understand the influence of the microstructure of Ni1-x-yCoxMy(OH)2 on the electrochemical properties of LiNi1-x-yCoxMyO2 cathode materials, so as to optimize the production process of preparing high-performance cathode precursors. In this review, we summarize recent advances in the research and development of Ni-rich cathode precursor materials. Firstly, the challenges faced by the Ni-rich hydroxide precursor materials are presented, including the effect of primary particle morphology and arrangement on the electrochemical performance of cathode materials, the influence of secondary particle morphology on lithium insertion reactions in cathode, and the effect of particle size on the microcracking of single-crystal particles. Secondly, the presentation of the conventional co-precipitation reactor, the mechanism of precursor particle growth, and the influence of co-precipitation parameters are described in detail. Finally, the strategies are systematically discussed to solve the challenges of hydroxide precursors, such as the innovation and optimization on reactants, synthesis processes, and reaction equipment. To obtain satisfactory high-quality precursor materials, future work will require an in-depth understanding of the reaction mechanism, combined with simulation techniques such as flow field theory calculations to guide the synthesis of precursors. This review provides a comprehensive analysis of the current progresses on the producing technologies of high-performance cathode precursors and offers prospects for future industry developments.

Particle structure development during spray drying from a single droplet to pilot-scale perspective

Crucial for achieving premium agglomerated powder products through spray drying is that the primary particle morphology and the degree of agglomeration can be controlled. However, the costs of trial runs and the wide range of products properties complicate achieving this control of particle structure during spray drying. Single droplet drying approaches are employed to study the development of the primary particle morphology and the collision behavior of droplets under well-defined conditions. These studies shed light on the underlying mechanisms but have been related less often to realistic drying and especially agglomeration. This review focuses on the potential and limitations of single droplet drying approaches to unravel the evolution of primary particle morphology and nozzle-zone agglomeration phenomena during spray drying. We discuss advances in single droplet drying approaches and how to combine these with pilot-scale spray drying to obtain the desired particle structures. • A wide range of SDD techniques exist, each providing their own benefit. • Collision behavior of droplets can be studied by modified SDD approaches. • Particle morphology development can only be studied for individual particles. • Pilot scale equipment is required to study full nozzle zone agglomeration.

The combined effect of rapid solidification and phosphor addition on the microstructure of hypereutectic A390 alloys

The influence of the combined effect of rapid solidification and phosphor addition on the morphology of primary silicon particles in A390 Al-Si alloy has been investigated by using light optical microscope (LOM). The P as modifier element was added in the shape of copper phosphor (Cu3P) master alloy. The results show that as the solidification rate increases, the size of primary silicon particles in A390 alloy reduces and the morphology of these particles evolve from plate-like to the fine nodular shape. The rapid solidification has a significant improvement on the refining performance of P to modify and refine the primary Si particles in A390 alloy. It is suggested that the refining performance of P in Cu3P master alloy is related to the formation the AlP particles which act as a heterogeneous nucleation. This affects the solidification rate and restricts the Si phase's growth.

High-Performance Ni-Rich Cathodes through Precision Control for Electric Vehicle Batteries

Li-ion batteries (LIBs) become the main portable energy source for electric vehicles (EVs) owing to their high energy and power densities as compared to those of other forms of secondary batteries. As the overall performance and cost of LIBs are largely determined by the cathode material, recent research has heavily focused on developing high-capacity cathode materials. However, chasing high-energy-density without compromising service life is very challenging. Among the available cathode materials for LIBs, layered Li[Ni1-x-yCox(Mn or Al)y]O2 (NCM or NCA) is the material of choice owing to its high theoretical capacity of 275 mAh g−1. The demand for higher energy density at a lower cost has pushed the Ni content to approach 90% because Ni is in charge of energy density in NCM and NCA cathode. The inclusion of more Ni in the NCM and NCA cathodes has significant benefits in LIB energy density and cost, as it concomitantly reduces the content of expensive Co. However, the increase in Ni content sacrifices cycling and thermal stability due to the high reactivity of Ni. Such a trade-off between energy density and stability becomes increasingly severe with increasing Ni content. Capacity fading of Ni-rich NCM and NCA cathodes, especially above Ni 80%, largely originates from microcracking which exposes a large portion of the cathode interior to deleterious electrolyte attack. To suppress the development of microcracks on cathode materials, Ni-rich cathode materials should guarantee mechanical stability even in highly charged states. In this presentation, Ni-rich layered cathodes through precision control are presented. One approach is an optimization of both the crystal structure and primary particle morphology by introducing high valence ions. Another strategy is to develop concentration gradient (CG) cathodes with rod-shaped primary particles that are elongated along the radial direction. The CG cathodes are further optimized via high-valence ion doping thereby preserving the microstructure until the cathode attains optimal crystal structure via the reduction of cation mixing. These cathodes exhibit outstanding performance in long-term cycling tests.

Morphology of Transition Metal Carbonate Cathode Precursors

Increasing the capacity of cathode materials used for lithium-ion batteries is desirable, as it ultimately enhances the energy density. Due to their lower cost and reversible cycling capacity of 250 – 300 mAh/g, Li- and Mn-rich LMR-NMC oxides are strong candidates as next generation cathodes used in lithium-ion batteries. Apart from the atomic structure, morphology of the cathode particles also influence their performance. LMR-NMC cathode particles are usually constructed through a two-step cathode fabrication process, which involves initial coprecipitation of the Mn-rich carbonate based cathode precursors, and later calcination of these precursors with a lithium salt at elevated temperatures. The secondary particles generally maintain their as precipitated precursor morphologies even after high temperature calcination. Even though the primary particles do change their size during calcination, the rate of oxidation and lithiation experienced by the transition metal precursors depend substantially on the primary particle morphology. Hence, it is critical to understand and control both the primary and secondary particle morphologies obtained after the coprecipitation process. In the present context, carbonate based NMC cathode precursors containing only Mn, only Ni and only Co, is precipitated, along with equal amount of the transition metals (Ni0.33Mn0.33Co0.33CO3), using conventional batch reactors. NH4HCO3 is used as the source of carbonate anions during the coprecipitation process, and the entire reaction is conducted at 50°C. The obtained particle morphologies for different transition metals are shown in Figure 1(a) as visualized using high resolution TEM techniques. Except MnCO3, all other transition metals demonstrate aggregated morphologies, which most probably form through surface growth mechanisms. Competition between growth rate and surface energies that leads to the formation of single crystalline particles for MnCO3, and particulate features for other transition metals, are demonstrated in Figure 1(b). Multiscale computational methodologies are developed to elucidate the impact of reaction kinetics and thermodynamics on determining the overall primary and secondary particle morphologies. Influence of transition metal content and ammonia concentration in determining the final particle size and size distribution will be discussed as part of this study. Figure 1

Recent Advances Towards Practical LiNiO2 Cathode Materials: Optimised Calcination and Modification with W Via a Single Step Synthesis Route

LiNiO2 has been long considered as a promising cathode material owing to its high practical energy density [1,2]. However, structural and surface instabilities, coupled with complexities in the synthesis, have thus far prevented its commercialisation [3]. In this talk I will review our recent work towards the use of LiNiO2 as an actual cathode solution, via carefully controlled calcination conditions [4,5] and stabilization especially in terms of elemental substitution (doping) [6,7], but also of protective surface coating.To address issues with the material’s stability during synthesis and cycling, the use of an ammonium tungstate flux to modify both the LiNiO2 crystal structure and primary particle morphology without introducing additional steps into the synthesis will be discussed here in particular detail. The successful preparation of LiNiO2 modified with an industrially relevant amount of W (< 5 mol %) was confirmed using a combination of electron microscopy and synchrotron-based X-ray diffraction (XRD). Refinement of structural models against the data suggests tungsten dopant ions occupy the Ni site and concurrently induce migration of Ni2+ to the Li sites. Moreover, W enrichment at grain boundaries has been observed under some of the synthesis conditions. Variable temperature XRD was used to highlight the improved stability of the W-doped materials during the calcination at high temperatures. Electrochemical characterisation shows that W-doped LiNiO2 offers improved cycle life at the expense of little specific capacity. The structural consequences of tungsten doping on the behaviour of the material during electrochemical cycling was also investigated using operando XRD, showing reduced mechanical stress upon cycling. In conclusion, we will show that LiNiO2 modified by W with a simple route and no additional processing steps exhibits structural stability at high temperatures, offering a path towards the reliable synthesis of LiNiO2 with controlled morphology, improved chemomechanics and longer cycling life. Reference s : [1] Dahn et al., Structure and Electrochemistry of Li1+-yNiO2 and a New Li2NiO2 Phase with the Ni(OH)2 Structure, Solid State Ionics 1990, 44 (1-2), 87-97.[2] Rougier et al., Optimization of the composition of the Li1-zNi1+zO2 electrode materials: Structural, magnetic, and electrochemical studies, Journal of the Electrochemical Society 1996, 143 (4), 1168-1175[3] Bianchini et al., There and Back Again-The Journey of LiNiO2 as a Cathode Active Material. Angew. Chem., Int. Ed. 2019, 58, 10434−10458.[4] Kurzhals et al., The LiNiO2 Cathode Active Material: A Comprehensive Study of Calcination Conditions and their Correlation with Physicochemical Properties. Part I. Structural Chemistry, Journal of the electrochemical society, 2021, 168 (11) 110518.[5] Riewald et al., The LiNiO2 Cathode Active Material: A Comprehensive Study of Calcination Conditions and their Correlation with Physicochemical Properties. Part II. Morphology, Journal of the electrochemical society, 2022, 10.1149/1945-7111/ac4bf3[6] Goonetilleke et al., Single step synthesis of W-modified LiNiO2 using an ammonium tungstate flux, Journal of Materials Chemistry A 2022, 10.1039.D1TA10568J.[7] Weber et al., Tracing Low Amounts of Mg in the Doped Cathode Active Material LiNiO2, Journal of the electrochemical society, 2022, 10.1149/1945-7111/ac5b38.

High-rate Ni-rich single-crystal cathodes with highly exposed {0 1 0} active planes through in-situ Zr doping

Nickel (Ni)-rich cathodes with high energy density will play a crucial role in the rapidly growing electric vehicles sector. However, the large-scale application of Ni-rich cathodes is still limited by structural instability and severe capacity decay. Even though the construction design of single-crystal cathodes alleviates these defects, the sluggish lithium ion (Li+) diffusion between the larger single-crystal particles restricts its rate performance. We propose an in-situ zirconium (Zr) ion doping strategy to modulate the primary particle morphology of precursors and achieve their corresponding single-crystal cathodes with highly exposed {010} planes. The high percentage of {010} planes will deliver more Li+ diffusion channels and improve the transportation kinetics. Moreover, the homogeneous doping of Zr inside the bulk phase will significantly suppress the anisotropic shrinkage of c-axis and maintain an intact internal structure, thus preventing the accumulation of rock-salt phases. As a result, the Zr-doped single-crystal cathode exhibits excellent cycling stability, whether at 25 ℃ or 45 ℃. More importantly, the rate performance of cathodes has been remarkably enhanced after Zr modification. At the ultra-high rate of 10 C, it can maintain a high specific capacity of 121.4 mAh g−1 (81.8 % of capacity retention) after 250 cycles in the 3.0–4.3 V range.

Study on the preparation technology of centrifugal Al-18Si-X composite reinforced with in situ particles

Al-18Si-X (X=Mg, Ti, Ni) composite tubular castings were prepared by centrifugal casting. The microstructure of cylindrical casting of Al-18Si-X composite was observed along the radial direction, and the segregation behavior and distribution characteristics of primary particles formed in different alloys under the action of centrifugal field were studied. The results show that the in situ particles in Al-18Si-7Mg, Al-18Si-7Ti, and Al-18Si-7Ni tubular castings have different segregation behaviors under the action of centrifugal field, which results in the formation of particle reinforcing layers in different regions of the castings. It is found that the volume fraction, size and particle morphology of primary particles in particle reinforcement layer of different castings are different.

(Digital Presentation) Modifying LiNiO2 with W Via a Single Step Synthesis Route

LiNiO2 has been long considered as a promising cathode material owing to its high practical energy density. However, structural and surface instabilities, coupled with complexities in the LiNiO2 synthesis, have thus far prevented its commercialisation. To address issues with the material’s stability during synthesis and cycling, the use of an ammonium tungstate flux is demonstrated here to modify both the LiNiO2 crystal structure and primary particle morphology without introducing additional steps into the synthesis. The successful preparation of LiNiO2 modified with an industrially relevant amount of W (< 5 mol %) was confirmed using a combination of electron microscopy and synchrotron-based X-ray diffraction (XRD). Refinement of structural models against the data suggests tungsten dopant ions occupy the Ni site and concurrently induce migration of Ni2+ to the Li sites. Moreover, W enrichment at grain boundaries has been observed under some of the synthesis conditions. Variable temperature XRD was used to highlight the improved stability of the W-doped materials during the calcination at high temperatures. Electrochemical characterisation shows that W-doped LiNiO2 offers improved cycle life at the expense of little specific capacity. The structural consequences of tungsten doping on the behaviour of the material during electrochemical cycling was also investigated using operando XRD, showing reduced mechanical stress upon cycling. In conclusion, we will show that LiNiO2 modified by W with a simple route and no additional processing steps exhibits structural stability at high temperatures, offering a path towards the reliable synthesis of LiNiO2 with controlled morphology, improved chemomechanics and longer cycling life.

Evolution of a Radially Aligned Microstructure in Boron-Doped Li[Ni0.95Co0.04Al0.01]O2 Cathode Particles.

Boron (B) (1.5 mol %) is introduced into Li[Ni0.95Co0.04Al0.01]O2 (NCA95) to create a radially oriented microstructure with a strong crystallographic texture. The cathode microstructure allows dissipation of the abrupt lattice strain near the charge end and improves the cycling stability of the NCA95 cathode (88% capacity retention after 100 cycles at 0.5 C). Transmission electron microscopy (TEM) analysis of the B-doped NCA95 cathode during lithiation reveals that the highly oriented microstructure is provided by a hydroxide precursor. Boron prevents random agglomeration of the primary particles and keeps them elongated through (003) faceting. The selected-area electron diffraction analysis shows that the structure of the lithiated oxide undergoes subtle structural changes even after the crystal structure is fully converted from P3̅m1 to R3̅m at 600 °C. Li+/Ni2+ intermixing is prevalent due to the slow oxidation of Ni2+ to Ni3+. Li+ and Ni2+ do not randomly occupy the Ni and Li layers; instead, these ions occupy their sites in an ordered pattern, forming a superlattice. The superlattice gradually disappears as the lithiation temperature is increased. One peculiar structural feature observed during lithiation is the prevalence of twin defects that preexist in the hydroxide precursor as growth twins. The twin defects, which could serve as nucleation sites for intraparticle cracks, also gradually anneal out during lithiation. TEM analysis substantiates the importance of the hydroxide precursor microstructure in a coprecipitation process and provides a basis for choosing the appropriate lithiation temperature and soaking time to obtain the desired cathode structure and primary particle morphology.