Surface Modification Of Materials Research Articles

A novel modified polydopamine based on melanin-like materials for antibacterial, hydrophobic, and ultraviolet protective of textiles

The development of environmentally friendly multifunctional auxiliaries for textile modification is the focus of attention in textile industry in recent years. Polydopamine is an important biological macromolecule and widely used in biomedicine, nanomaterials, material surface modification and other fields. In this study, the novel multifunctional melanin-like nanoparticles (Nha-PDA NPs) were prepared and used for antibacterial, hydrophobic, and UV protective of textiles. Nha-PDA NPs were prepared with dopamine (DA) and n-hexylamine (Nha) by simple autoxidation copolymerization. Nha-PDA NPs were bound to the fabric surface through the PDA structure in Nha-PDA NPs that has been widely confirmed to have strong adhesion on the surface of many materials. The modified fabrics, Nha-PDA NPs@Cotton, had good hydrophobic, antibacterial and UV protective properties. The static water contact angles of the modified fabrics could reach 120°. The antibacterial rates of Nha-PDA NPs@Cotton against E. coli and S. aureus were above 85 %. The maximum UPF value of the modified cotton was 362, indicating that the ultraviolet protection performance was excellent. The fabric modified with multifunctional melanin-like nanoparticle provides a green way for the multifunctional modification of textiles.

Current developments and future perspectives of nanotechnology in orthopedic implants: an updated review.

Orthopedic implants are the most commonly used fracture fixation devices for facilitating the growth and development of incipient bone and treating bone diseases and defects. However, most orthopedic implants suffer from various drawbacks and complications, including bacterial adhesion, poor cell proliferation, and limited resistance to corrosion. One of the major drawbacks of currently available orthopedic implants is their inadequate osseointegration at the tissue-implant interface. This leads to loosening as a result of immunological rejection, wear debris formation, low mechanical fixation, and implant-related infections. Nanotechnology holds the promise to offer a wide range of innovative technologies for use in translational orthopedic research. Nanomaterials have great potential for use in orthopedic applications due to their exceptional tribological qualities, high resistance to wear and tear, ability to maintain drug release, capacity for osseointegration, and capability to regenerate tissue. Furthermore, nanostructured materials possess the ability to mimic the features and hierarchical structure of native bones. They facilitate cell proliferation, decrease the rate of infection, and prevent biofilm formation, among other diverse functions. The emergence of nanostructured polymers, metals, ceramics, and carbon materials has enabled novel approaches in orthopaedic research. This review provides a concise overview of nanotechnology-based biomaterials utilized in orthopedics, encompassing metallic and nonmetallic nanomaterials. A further overview is provided regarding the biomedical applications of nanotechnology-based biomaterials, including their application in orthopedics for drug delivery systems and bone tissue engineering to facilitate scaffold preparation, surface modification of implantable materials to improve their osteointegration properties, and treatment of musculoskeletal infections. Hence, this review article offers a contemporary overview of the current applications of nanotechnology in orthopedic implants and bone tissue engineering, as well as its prospective future applications.

Polysaccharides screening for pulmonary mucus penetration by molecular dynamics simulation and in vitro verification

Mucus penetration is one of the physiologic barriers of inhalation and nanocarriers can effectively facilitate the permeation of drugs. The interactions between the nanocarriers and mucin are crucial for penetration across the mucus layer on the respiratory tract. In this study, we proposed a molecular dynamics (MD) simulation method for the screening of polysaccharides that acted as the surface modification materials for inhalable nano-preparations to facilitate mucus penetration. MD revealed all-atom interactions between the monomers of polysaccharides, including dextran (DEX)/hyaluronic acid (HA)/carboxymethyl chitosan (CMCS) and the human mucin protein MUC5AC (hMUC5AC). The obtained data showed that DEX formed stronger non-covalent bonds with hMUC5AC compared to HA and CMCS, which suggested that HA and CMCS had better mucus permeability than DEX. For the in vitro verification, HA/CMCS-coated liposomes and DEX/PEG-inserted liposomes were prepared. The results of mucin interactions and mucus penetration studies confirmed that HA and CMCS possessed the weakest interactions with mucin and facilitated the mucus penetration, which was in consistent with the data from MD simulation. This work may shed light on the MD simulation-based screening of surface modification materials for inhalable nano-preparations to facilitate mucus penetration.

Hydrophilic surface modification of polypropylene by AC-DBD and NS-DBD

Dielectric barrier discharge (DBD) is a method to modify material surfaces by creating low-temperature plasma at atmospheric pressure. However, in comparison to low-pressure discharge, atmospheric DBD has the drawback of uneven surface treatment due to the ease of forming filamentary channels. This limitation hinders the widespread application of DBD technology in material surface modification. In this study, the surface of polypropylene (PP) was treated using high frequency alternating current (AC) and nanosecond (NS) pulsed argon DBDs to improve surface hydrophilicity. The changes of the PP surface hydrophilicity and the treatment uniformity were characterized by water contact angle (WCA) measurement. The relationships between the DBD characteristics, the treatment effect and the treatment uniformity of the PP surface were investigated using electrical and optical diagnostic techniques. The PP material surfaces before and after plasma treatments were evaluated by the physical morphology and chemical composition measurements to examine the influence of DBD on the treatment effect and uniformity on the PP material surface. The findings show that the modification by AC-DBD reduces the WCA of PP material surface by 40°∼50° and exhibits a variance of 1.77, indicating an improvement in hydrophilicity to some extent. Furthermore, the modification by NS-DBD further decreases the WCA of PP material surface, reducing the variance to 1.14. Compared with AC-DBD, NS-DBD has a better uniformity, a higher concentration of active particles in plasma, a greater surface roughness of PP material after treatment, a better hydrophilicity and a more uniform effect with less energy consumption. The results are meaningful to improve the application of DBD in material surface modification and optimize the power source election and operation parameters.

Zwitterionic Tröger's Base Microfiltration Membrane Prepared via Vapor-Induced Phase Separation with Improved Demulsification and Antifouling Performance.

The fouling of separation membranes has consistently been a primary factor contributing to the decline in membrane performance. Enhancing the surface hydrophilicity of the membrane proves to be an effective strategy in mitigating membrane fouling in water treatment processes. Zwitterionic polymers (containing an equimolar number of homogeneously distributed anionic and cationic groups on the polymer chains) have been used extensively as one of the best antifouling materials for surface modification. The conventional application of zwitterionic compounds as surface modifiers is intricate and inefficient, adding complexity and length to the membrane preparation process, particularly on an industrial scale. To overcome these limitations, zwitterionic polymer, directly used as a main material, is an effective method. In this work, a novel zwitterionic polymer (TB)-zwitterionic Tröger's base (ZTB)-was synthesized by quaternizing Tröger's base (TB) with 1,3-propane sultone. The obtained ZTB is blended with TB to fabricate microfiltration (MF) membranes via the vapor-induced phase separation (VIPS) process, offering a strategic solution for separating emulsified oily wastewater. Atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle, and zeta potential measurements were employed to characterize the surface of ZTB/TB blended membranes, assessing surface morphology, charge, and hydrophilic/hydrophobic properties. The impact of varying ZTB levels on membrane surface morphology, hydrophilicity, water flux, and rejection were investigated. The results showed that an increase in ZTB content improved hydrophilicity and surface roughness, consequently enhancing water permeability. Due to the attraction of water vapor, the enrichment of zwitterionic segments was enriched, and a stable hydration layer was formed on the membrane surface. The hydration layer formed by zwitterions endowed the membrane with good antifouling properties. The proposed mechanism elucidates the membrane's proficiency in demulsification and the reduction in irreversible fouling through the synergistic regulation of surface charge and hydrophilicity, facilitated by electrostatic repulsion and the formation of a hydration layer. The ZTB/TB blended membranes demonstrated superior efficiency in oil-water separation, achieving a maximum flux of 1897.63 LMH bar-1 and an oil rejection rate as high as 99% in the oil-water emulsion separation process. This study reveals the migration behavior of the zwitterionic polymer in the membrane during the VIPS process. It enhances our comprehension of the antifouling mechanism of zwitterionic membranes and provides guidance for designing novel materials for antifouling membranes.

Non-contact humidity monitoring: Boosting the performance of all-printed humidity sensor using PDDA-modified Ti3C2Tx nanoribbons

Non-contact humidity monitoring can provide us with rich information about our bodies in a non-invasive way. However, this concept is hindered by the low sensitivity and slow response time of conventional humidity sensors. Herein, we employed two strategies, structural design and surface modification of MXene materials, to improve the sensitivity of MXene-based humidity sensors. A 3D porous structure was formed by the alkalinization treatment MXene, which facilitated rapid diffusion of water molecules along interlayer nanochannels and fast electron transport. Furthermore, the charged positively poly (diallyldimethylammonium chloride) (PDDA) was adsorbed onto the surface of the 3D skeleton through self-assembly to prepare a novel composite material KPMX. The loaded PDDA enhanced the interaction between MXene and water molecules, reducing the oxidation sensitivity of MXene. Additionally, the material was further formulated as inks with suitable viscosity and successfully used to produce a paper-based flexible humidity sensor through screen printing. Consequently, the KPMX sensor exhibited impressive potential in humidity sensing with high sensitivity (48813 %), rapid response/recovery time (8.794/2.656 s), and excellent stability. This work provided a practical strategy for non-contact humidity monitoring, including detecting the proximity of fingertips and changes in humidity in breathing patterns.

Strategies to Improve the Output Performance of Triboelectric Nanogenerators

AbstractTriboelectric nanogenerators (TENGs) can collect and convert random mechanical energy into electric energy, with remarkable advantages including broadly available materials, straightforward preparation, and multiple applications. Over the years, researchers have made substantial advancements in the theoretical and practical aspects of TENG. Nevertheless, the pivotal challenge in realizing full applications of TENG lies in ensuring that the generated output meets the specific application requirements. Consequently, substantial research is dedicated to exploring methods and mechanisms for enhancing the output performance of TENG devices. This review aims to comprehensively examine the influencing factors and corresponding improvement strategies of the output performance based on the contact electrification mechanism and operational principles that underlie TENG technology. This review primarily delves into five key areas of improvement: materials selection, surface modification, component adjustments, structural optimization, and electrode enhancements. These aspects are crucial in tailoring TENG devices to meet the desired performance metrics for various applications.

A pulsed bipolar current-mode power supply with high power factor in a single stage for dielectric barrier discharge application

Purpose Dielectric barrier discharge (DBD) is widely used in the treatment of skin disease, surface modification of material and other fields of electronics. The purpose of this paper is to design a high-performance power supply with a compact structure for excimer lamps in electronics application. Design/methodology/approach To design a high-performance power supply with a compact structure remains a challenge for excimer lamps in electronics application, a current-source type power supply in a single stage with power factor correction (PFC) is proposed. It consists of an excitation voltage generation unit and a PFC unit. By planning the modes of the excitation voltage generation unit, a bipolar pulse excitation voltage with a high rising and falling rate is generated. And a high power factor (PF) on the AC side is achieved by the interaction of a non-controlled rectifier and two inductors. Findings The experimental results show that not only a high-frequency and high-voltage bipolar pulse excitation voltage with a high average rising and falling rate (7.51GV/s) is generated, but also a high PF (0.992) and a low total harmonic distortion (5.54%) is obtained. Besides, the soft-switching of all power switches is realized. Compared with the sinusoidal excitation power supply and the current-source power supply, the proposed power supply in this paper can take advantage of the potential of excimer lamps. Originality/value A new high-performance power supply with a compact structure for DBD type excimer lamps is proposed. The proposed power supply can work stably in a wide range of frequencies, and the smooth regulation of the discharge power of the excimer lamp can be achieved by changing the switching frequency. The ideal excitation can be generated, and the soft switching can be realized. These features make this power supply a key player in the outstanding performance of the DBD excimer lamps application.

Surface structuring and in situ synthesis of nanoparticles by ultrashort laser processing on hydroxyapatite

Ultrashort laser pulses represent a versatile tool that finds application in a variety of fields allowing precise and controlled modification of any kind of materials. The material surface modification, by inducing the formation of micro and nanostructures or providing chemical changes, or its functionalization with other materials, in form of nanoparticles, strongly affects the behavior and performances of such materials. The surface structuring and the synthesis and deposition of metallic nanoparticles has both been obtained by laser exposure. The two processes are performed consecutively, on hydroxyapatite sample surface. The synthesis of silver nanoparticles (AgNPs) takes place on the sample surface, while immersed in a solution of silver nitrate (AgNO3), by laser-induced multiphoton photoreduction of silver ions (Ag+).

Investigation of electromagnetic wave absorption and anti-corrosion mechanism of multifunctional Ni/AlN composite coatings with core-shell structure by laser cladding

Developing efficient microwave absorbing materials (MAMs) suitable for prolonged use in marine environments is of great importance. Laser cladding serves as one of the new techniques for the material of surface modification and microwave-absorbing materials in the 3D printing. However, it is usually challenging to prepare materials that combine desirable printability, corrosion resistance, and microwave absorption properties using this technology. To enhance the microwave absorption of laser-clad Ni-based alloys, the method of impedance modulation was employed by incorporating ceramic powders with varying AlN content. The results show that Ni/AlN/MWCNTs composite functional materials with core-shell heterostructures were prepared under optimized laser processing parameters. This unique core-shell structure optimizes impedance matching increased polarization loss and multiple scattering to boost microwave absorption. The optimized 20wt% AlN content resulted in a minimum RL of -13.24dB at 13.86GHz, in addition, electrochemical tests showed that AlN enhanced the resistance to the corrosion medium transfer during the corrosion process, and the corrosion resistance of the Ni/AlN/MWCNTs composites material (self-corrosion current density (8.52 × 10-8), the charge transfer resistance (1.55 × 10-5)). Therefore, this work provides innovative theoretical and practical insight for the design and manufacture of advanced microwave-absorbing materials for harsh environments by laser melting technology.

The Role of Plasma Technology in surface modification of textiles

The Role of Plasma Technology in surface modification of textiles

Unraveling the complex infiltration and repairing behaviors in defect coatings

Organic coatings are commonly used to protect the metals or alloys from corrosion. However, defects such as scratches or natural aging of the coating can induce unexpected diffusion paths for the corrosive media, so the wettability of repairing liquids and the selection of suitable repairing liquids are crucial. In this study, we systematically investigated the capillary impregnation phenomenon by using liquids with various surface tensions and glass capillaries with different surface energies. We utilized this regularity to instruct the defects repairing process. By using an ultra-depth field microscope, scanning electron microscope, and electrochemical analysis, two kinds of repairing liquids, high surface tension liquid (HSTL) and low surface tension liquid (LSTL), were investigated for repairing man-made defects of coatings. Our results showed that the substrate and the surface energy of the liquids significantly influence the infiltration of the repair liquid. By effectively leveraging the relationship between the repair liquid and the substrate, the repair agent can not only establish a uniform and dense repairing layer but also notably enhance the corrosion resistance of the defective coating. This study provides valuable insights into the repairing of coating defects, as well as liquids transportation, microfluidic chip design, and surface modification of microporous materials.

Multi-ion magnetized sheath properties with non-extensive electron distribution

Magnetized plasma sheath plays an important role in semiconductor processing, material surface modification, film deposition, etc. In plasma experiments and discharge applications, multi-ion plasma consisting of more than two kinds of ions often exists. For a long range interacting plasma system, non-Maxwellian electrons can be described by the non-extensive distribution of Tsallis. In this work, a fluid model with one-dimensional spatial coordinates and three-dimensional velocity coordinates is established for the multi-ion plasma sheath. It is assumed that the electron velocity in the sheath follows a non-extensive distribution, and the background helium ions and different kinds of impurity ions are magnetized in a magnetic field with a certain tilt angle. The effects of non-extensive parameters, impurity ions and oblique magnetic field on the number density, velocity, wall potential and kinetic energy of ions in the multi-ion magnetic sheath are investigated by numerical simulation. The results show that in the helium-hydrogen or helium-argon mixed plasma sheath, the ionic velocity along the vertical wall direction decreases with the increase of the non-extensive parameters, the number density of ions and electrons in the sheath, the sheath thickness , and the kinetic energy of ions at the wall decrease. When the concentration of impurity ions increases, the kinetic energy of ions on the wall is independent of the type of ions. With the increase of magnetic field intensity, the number density of helium ions and the velocity along the vertical wall fluctuate along the sheath edge, and the fluctuation amplitude increases with the decrease of non-extensive parameters, while the heavy ions have no obvious fluctuation. In addition, the effects of the types and concentrations of impurity ions on the related properties of the sheath are also analyzed. With the increase of the magnetic field intensity, the number density and the velocity along the vertical wall direction fluctuate at the sheath edge, and the fluctuation amplitude increases with the decrease of the non-extensive parameter, whereas there are no significant fluctuations for heavy ions. In addition, when impurity ions are heavy ions, the absolute value of wall potential increases with the increase of impurity ion concentration and the decrease of non-extensibility parameters, and the kinetic energy of background ions increases at the wall surface. When the impurity ion is a light ion, the absolute value of the wall potential decreases with the increase of the impurity ion concentration and the decrease of the non-extensibility parameter, and the kinetic energy of the background ion at the wall decreases.

A review on the surface modification of materials for 3D-printed diagnostic devices.

Three-dimensional (3D) printing in tissue engineering and biosensing of analytes by using biocompatible materials or modifying surface structures is an upcoming area of study. This review discusses three common surface modification techniques, viz. alkaline hydrolysis, UV light photografting, and plasma treatment. Alkaline hydrolysis involves the reaction of an alkaline solution with the surface of a material, causing the surface to develop carboxyl and hydroxyl groups. This technique can enhance the biocompatibility, surface wettability, adhesion, printability, and dyeability of materials, such as acrylonitrile butadiene styrene (ABS), polycarbonate, and polylactic acid (PLA). This review also mentions details about some of the surface-modified 3D-printed diagnostic devices. Although most of the devices are modified using chemical processes, there are always multiple techniques involved while designing a diagnostic device. We have, therefore, mentioned some of the devices based on the materials used instead of categorising them as per modification techniques. 3D printing helps in the design of sophisticated shapes and structures using multiple materials. They can, therefore be used even in the design of microfluidic devices that are very useful for biosensing. We have also mentioned a few materials for printing microfluidic devices.

Surface modification of particles in a photochemical fluidized bed

Different techniques have been recently studied to promote the surface modification of materials. Surface modifications are used to improve the performance of materials in diverse areas, such as chemical processes, pharmaceutical industry and agriculture. Despite the considerable work in the literature on the subject, the experiments carried out were always conducted with small samples of the materials, and the performance of the treatment on a larger scale has yet to be evaluated. This work aimed to make the surface modification of particles of different materials by UV-assisted treatment in a photochemical fluidized bed. The purpose was to verify the feasibility of treating particles with UV radiation on a larger scale, something not yet found in the literature. The analyzed materials were two polymers and four types of forage seeds. The effect of UV radiation on the surface was checked using the water contact angle (WCA) and FTIR analysis. The treated seeds were also submitted to the Standard Germination Test (SGT) to verify eventual physiological damages and possible beneficial effects of the treatment. The results indicated a significant decrease in the contact angle of the treated particles of all materials because of the incorporation of oxygenated groups on their surface. In turn, the SGT pointed out not only that the seeds were not damaged by radiation but also that there was a significant increase in the agronomic index for two of the species studied. The data obtained in this work showed that the photochemical fluidized bed proved a viable way to carry out the surface treatment of particles with UV radiation, making it possible to conduct the process on a larger scale.

Electrochemical modification of the carbon material surface by hydroxyl groups

Electrochemical modification of the carbon material surface by hydroxyl groups

Activation of Dopamine Receptor D1 and Downstream Cellular Functions by Polydopamine.

Polydopamine is a remarkable molecule that has gained considerable attention for its role in material surface modification, leading to an abundance of research in the biomaterial domain. While its widespread use is well documented, the molecule's potential cellular interactions have been less explored. In particular, dopamine serves as a neurotransmitter and a hormone that interacts with dopamine receptors in cells. Our study sheds light on the previously unexamined interaction between polydopamine and dopamine receptor D1 (DRD1). We discovered that polydopamine, along with its derivatives, such as levodopa and catechol, can activate DRD1─a function previously attributed solely to dopamine. Moreover, we found that polydopamine has the ability to influence cell behavior through the cAMP/PKA pathway, thereby affecting RhoA activity and stress fiber formation. These observations invite further consideration regarding the biological safety of polydopamine in biomedical contexts and also open avenues for new research directions in designing bioactive functional materials.

Effect of Oxygen Functionalities inside Carbon Micropore on Lithium-Sulfur Battery Performance

Introduction Lithium-sulfur batteries (LSB) using a sulfur cathode with a high specific capacity (1672 mAh g-1) have been regarded as one of the most promising candidates for large-scale energy storage systems, while the sulfur cathode's drawback hinders the commercial application of LSB. Soluble Li2Sx (x = 4 – 8) generated during a charge-discharge process dissolves into electrolytes, which induces LSB's self-discharge and capacity decay. The main efforts to overcome this issue have been on physical confinement of sulfur in the pores of porous carbons [1,2]; however, carbon materials, being non-polar in nature, interact weakly with the polar Li2Sx, which still leads to low cycle stability of LSB. Hence, the surface modification to porous carbon, which provides polar-polar interaction between the carbon surface and Li2Sx, has been performed, suppressing the Li2Sx dissolution and improving LSB's performance [1,3].On the other hand, we reported that polar-oxygen functionalities on microporous carbon (MC), which are generated with oxidants, significantly improve the discharge capacity of LSB [4]. The formation of Li2Sx (x = 4 – 8) is inhibited in micropores (pore diameter < 2 nm) [5]; therefore, the oxygen functional groups probably improve the discharge capacity of LSB assembled with a MC-sulfur composite cathode due to factors other than the suppression effect of Li2Sx dissolution. Our previous study revealed that oxygen functionalities on the MC surface contribute to the enhanced electrochemical performance of the LSB by preventing electrolyte decomposition and thus decreasing the resistance of the cathode electrolyte interface (Rcei) [6]. However, the ratio of Rcei to the total resistance of the LSB is small; the oxygen functional groups would improve the performance of LSB by affecting other resistance. Herein, we investigate the effect of surface oxygen functionalities on charge transfer resistance (Rct) and Li+ diffusion of LSB. Our report would provide deep insight into the surface modification of carbon materials as LSB’s cathode. Method 2.1. Preparation of Oxidized MC-Sulfur composite MC was added into 69 wt.% HNO3 and refluxed at 120ºC for 2 h (Ox MC). Washed and dried Ox MC was mixed with sulfur at a weight ratio of 48: 52. The mixture was heated at 155ºC for 5 h (Ox MC-S). 2.2. Assembling of Cells To obtain the Ox MC-S cathode, the slurry prepared by mixing the Ox MC-S, acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a weight ratio of 89: 5: 3: 3 was coated on an Al foil. The cells with the Ox MC-S cathode and Li metal anode were assembled in a glove box. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (HFE) = 10: 8: 40 (by mol) was used as the electrolyte. 2.3. Activation Energy Measurement with Electrochemical Impedance Spectroscopy (EIS) To elucidate the effect of oxidation treatment on the Rct and Warburg impedance (Rw) of Li-S batteries, activation energy measurement was carried out at 2.5 V in the 50th charging process. The temperature range was 0 – 25°C, and the alternating current voltage amplitude was 10 mV. Rw was investigated with the calculation of the Warburg coefficient (σ). Major results and conclusion The activation energy of Rct (Ect) and σ were determined to investigate the effects of oxygen functional groups formed at MC surfaces on charge transfer processes and Li+ diffusion. While Ect increased from 0.65 to 0.72 eV by oxidation treatment, the frequency factor increased from 17.7 to 20.9; this indicates that the oxygen functional groups improve the number of reaction sites where three substances (carbon, active material, and electrolyte) come into contact with each other. The σ of MC-S and Ox MC-S were 281.2 and 178.9 Ω s-1/2, respectively. Therefore, a decrease in Rw due to oxygen functional groups was suggested.The charge transfer process and Li+ diffusion occur inside the microporous carbon particles where the confined sulfur is present. We processed the Ox MC-S particle from the cathode after the 50th charging using focused ion beam (FIB) milling to obtain a cross-section and observed it with STEM-EELS. This result will also be reported in our presentation.This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING [JPMJAL1301])” from JST.[1] X. Ji et al., Nat. Mater., 8 (2009) 500.[2] T. Takahashi et al., Prog. Nat. Sci., 25 (2015) 612.[3] L. Yoshida et al., Electrochim. Acta, 429 (2022) 141000.[4] S. Okabe et al., Electrochemistry, 85 (2017) 671.[5] Y. Xiao et al., RSC Adv., 10 (2020) 39875.[6] L. Yoshida et al., 242nd ECS Meeting s, Z01-2299 (2022).

Flux Growth and Surface Modification of Highly-Crystalline Active Materials and Solid Electrolytes for High Performance Libs

Materials for energy devices are often multicomponent with a number of interfaces and heterojunctions. In particular, lithium-ion batteries (LIBs) have been studied extensively because of their potential use as power sources. Recently, there has been a particular focus on all-solid-state LIBs (and high-performance LIBs). They have attracted considerable attention due to their high energy densities, which are the result of device miniaturization, and high safety due to their non-flammability. However, there is an extremely large innovation gap between general purpose LIBs and all-solid-state LIBs due to difficulties in the smooth transfer of lithium ions, i.e., the diffusion of lithium ions and electrons are disturbed at the interfaces of different solid materials. Therefore, we have tried to control and design their interfaces between active materials and solid electrolytes and fabricate materials for all-solid-state LIBs based on crystal science and engineering. Our research group has developed flux crystal growth and its extended methods for the preparation of high crystalline materials. Flux method is a liquid phase crystal growth in which idiomorphic highly crystalline particles can be obtained below the melting point of the target. Therefore, outmost crystal planes are tuned by our techniques where they have desired various ion and electron paths (i.e., hyper-spaces). In addition, the grown crystals are expected to have high crystallinity because diffusion and rearrangement of atoms easily occurred compared to conventional particle fabrication methods. Recently, we have developed a flux method to fabricate crystal layers on various substrates, which is called "flux coating method". For example, the target LIB-based materials are cathode active materials such as LCO, LNM, NCM, LFP and so on, anode active materials such as LTO, TNO and the related materials, and solid electrolytes such as LLZ, LLT, LLN, etc. and their crystal layers. Furthermore, their surface conditions are precisely controlled in our laboratory. Details on material design and hyperspace control of flux-grown crystalline particles and crystal layers via flux-related techniques will be reported at the 244th ECS Meeting.

Solution-Based Synthesis of Cathode Materials for Lithium Ion Batteries

Electrochemical energy storage is expected to make an important contribution to combating global climate change, e.g. via electric vehicles and stationary storage. Currently, lithium-ion batteries are the most prominent candidate for rechargeable batteries to be used in this respect. However, performance of lithium-ion batteries is strongly influenced by the active material at the cathode side, which is often a complex multi-metal oxide. Such a material's properties are dictated by the fabrication method. The design of an appropriate synthesis strategy is then logically also aimed at optimal material properties. However, the design strategy should also take into account green chemistry principles, such as atom economy and energy efficiency. Solution-based routes towards (multi)metal oxide synthesis provide a large diversity of routes and therefore a strong versatility in their design. In this contribution, two groups of routes will be discussed: aqueous solution-gel and coprecipitation routes. The aqueous solution-gel route encompasses three stages: precursor solution synthesis, in which the metal ions are stabilized by complexation with carboxylate ligands, gelation to form an amorphous precursor gel in which the metal ions are homogeneously mixed, and decomposition into the final metal oxide. In this route, precipitation is to be avoided, since it would introduce inhomogeneities. In contrast, the coprecipitation route is entirely based on the formation of insoluble solid precipitates, which can be further transformed in a solid state reaction into lithiated compounds. Whereas solution-gel is ideally suited for complex metal oxides with a large number of metal ions, coprecipitation of many different metal ions at the same time can be challenging. On the other hand, the atom efficiency of the latter can be very high which is attractive for upscaling. Certainly, both of these routes have a high versatility because of the flexibility in compositions (starting products, solvents, ...) and conditions (temperature, time, ...) during the synthesis.In this presentation, an overview will be given of the application of these synthesis routes to the synthesis and/ or surface modification of various cathode materials for lithium ion batteries, which are of general interest and are ranging from Ni-rich compositions of NMC (NMC622), to lithium manganese rich NMC and to Co-free compositions such as LNMO and Li rich LMO. First, the classic NMC 622 is surface modified by a TiOx via a sol-gel route, leading to the formation of core-shell structured particles. The presence of TiOx improved the rate performance and electronic conductivity of the cathode material, and led to a higher initial coulombic efficiency and lower ageing rates in full cells with LTO. Furthermore, layered Li-rich/Mn-rich (LMR-)NMC, which is interesting because of its remarkably high specific discharge capacity was synthesized by two different routes, solution-gel and coprecipitation. It was shown that the solution-gel material in this case had a retarded voltage fade but larger capacity fade than the coprecipitated material. This was correlated to differences in particle morphology and the presence of Ni-enriched spinel-type surface layer. Furthermore, the effect of Sn4+ substitution in the LMR-NMC was investigated. The solubility of Sn4+ substituting for Mn4+ turned out to be a limiting factor here, and could not prevent the voltage fade sufficiently. Finally, we turned to Co-free cathode compositions. LiNi0.5Mn1.5O4-delta was prepared by an aqueous solution-gel route, which allowed to tune the particle size (a few µm versus 70 µm) and morphology. This led to optimized initial discharge capacity and its retention. Finally, Ti4+ substituted Li2MnO3 was synthesized as well via an aqueous solution-gel method. The substitution was shown to improve the structural stability, and galvanostatic cycling hinted at a delayed oxygen release during the first 10 cycles, however, followed by pronounced oxygen redox activity.In conclusion, solution-based routes are highly versatile and provide many opportunities to synthesize cathode materials for lithium ion batteries.