nano-Si Particles Research Articles

Lithium-Ion battery silicon Anodes: Surface engineering with novel additives for enhanced ion and electron transport

Silicon (Si) stands as a promising candidate for high-capacity anode materials in the next-generation lithium-ion batteries (LIBs) due to extremely high specific capacity. However, silicon application is hindered by its inherently poor electron and ion conductivities, as well as structural instability during the repeated charging/discharging. To address these challenges, a novel functional surface modification agent, diethylenetriaminepenta(methylenephosphonic) acid (DTPMP), was decorated on the surface of silicon particles for the first time. The experimental results demonstrate that the DTPMP effectively enhances the cohesion between nano Si particles. This study combines experimental observations with theoretical calculations to analyze the nucleophilic and electrophilic sites of DTPMP and carboxymethyl cellulose (CMC), elucidating the existence state of DTPMP on the nano Si surface. Furthermore, by examining the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), along with the electrostatic potential (ESP) of DTPMP and solvent molecules in conjunction with Li+, the impact of the phosphate group on the diffusion of Li+ and electrons at the nano Si surface was studied. The electron density difference (EDD) maps for DTPMP and CMC reveal that DTPMP exhibits a more pronounced response in the presence of an electric field, suggesting its enhanced role in facilitating Li+ diffusion. This research offers a novel perspective on enhancing the electrochemical performance of nano Si surfaces, paving the way for the development of advanced LIBs with improved energy storage capabilities.

Simple and Safe Synthesis of Yolk-Shell-Structured Silicon/Carbon Composites with Enhanced Electrochemical Properties.

With its substantial theoretical capacity, silicon (Si) is a prospective anode material for high-energy-density lithium-ion batteries (LIBs). However, the challenges of a substantial volume expansion and inferior conductivity in Si-based anodes restrict the electrochemical stability. To address this, a yolk-shell-structured Si-carbon composite, featuring adjustable void sizes, was synthesized using tin (Sn) as a template. A uniform coating of tin oxide (SnO2) on the surface of nano-Si particles was achieved through a simple annealing process. This approach enables the removal of the template with concentrated hydrochloric acid (HCl) instead of hydrofluoric acid (HF), thereby reducing toxicity and corrosiveness. The conductivity of Si@void@Carbon (Si@void@C) was further enhanced by using a high-conductivity carbon layer derived from pitch. By incorporating an internal void, this yolk-shell structure effectively enhanced the low Li+/electron conductivity and accommodated the large volume change of Si. Si@void@C demonstrated an excellent electrochemical performance, retaining a discharge capacity of 735.3 mAh g-1 after 100 cycles at 1.0 A g-1. Even at a high current density of 2.0 A g-1, Si@void@C still maintained a discharge capacity of 1238.5 mAh g-1.

Improving the comprehensive mechanical property of the AlSi10Mg alloy via parameter adaptation of selective laser melting and heat treatment

In this work, the AlSi10Mg alloys with distinct molten pool structures, namely fish-scale and lamellar, were fabricated by using selective laser melting (SLM) technology. The effects of solid solution temperature on the microstructural evolution and mechanical properties of the two types of alloys were systematically investigated. The relationship among initial structure, heat treatment and mechanical properties was revealed. The experimental results showed that for the alloy with fish-scale structure, Si diffused more easily after solid solution treatment due to the finer eutectic network, resulting in a larger Si particle size. At 510 °C, the nano Si particles in the fish-scale sample basically disappeared, but a small amount of nano Si particles still existed in the lamellar sample, leading to a bimodal distribution in the Si particle size. Different sizes and distributions of Si particles present different strengthening mechanisms and affect the nucleation and growth of recrystallized grains in the α-Al matrix, leading to significant differences in mechanical properties. The strength of the lamellar sample decreased with increasing the temperature, and the abnormally growth of grains could be found after being treated at 510 °C, resulting in a poor mechanical property. The strength of fish-scale sample first decreased and then increased with the increase of solid solution temperature. When the alloy with fish-scale structure was solid solution treated at 510 °C, Si particles could promote the nucleation of recrystallized grains but hinder their growth, and the ultimate tensile strength decreased from 478.8 MPa of SLMed state to 393.4 MPa, a reduction of 17.8%, while the elongation increased from 7% to 21%, an increase of 300%, showing an excellent overall mechanical property. Therefore, the present study demonstrates that adjusting the SLMed molten pool structure and heat treatment parameters is necessary to obtain a good combination of microstructure and mechanical property.

Synthesis of a Yolk-Shell Nanostructured Silicon-Based Anode for High-Performance Li-Ion Batteries

Silicon is a desirable anode material for Li-ion batteries owing to its remarkable theoretical specific capacity of over 4000 mAh/g. Nevertheless, the poor cycling performance of pure Si electrodes caused by dramatic volume expansion has limited its practical application. To alleviate the adverse effects of Si expansion, we have synthesized anode materials of nano-Si particles trapped in a buffering space and outer carbon-based shells (Si@Void@C). The volume ratio of Si nanoparticle to void space could be adjusted accurately to approximately 1:3, which maintained the structural integrity of the as-designed nanoarchitecture during lithiation/delithiation and achieved a notable specific capacity of ~750 mAh/g for as-prepared half-cells. The yolk-shell nanostructure alleviates volumetric expansion on both material and electrode levels, which enhances the rate performance and cycling stability of the silicon-based anode.

Inlaying Silicon in SiC-Derived Graphite with Unique Cavity Structure as a High-Capacity Anode for Li-Ion Batteries

Silicon-based anode in Li-ion batteries has received much attention due to its extremely high theoretical capacity which can support high-energy-density battery system. However it suffers seemingly insurmountable barriers including volume expansion and capacity fading during repetitive cycling. In this work, we demonstrated a new kind of silicon/carbon (Si/C) composite design to address the issues in the silicon-based anode application via building a three-dimensional structure of nano Si and carbide-derived-graphite (CDG). Unique cavity-structured CDG made from SiC powder via scalable high temperature treatment, could supply a conductive host for the well-dispersed nano Si particles. CDG/Si composite get improved cycle stability and maintained high capacity of 637 mAh g−1 after 500 cycles. Rate performance of CDG/Si was also enhanced, which should be attributed to good electrolyte accessibility and short ion diffusion distance of CDG to enhance electrode kinetics. In addition, CDG was verified to accommodate higher content of Si of 60%, to achieve higher capacity of 1800 mAh g−1. This work provided a good alternative of carbon matrix for Si/C anode, and it is anticipated that this kind of carbide derived graphite might be of great interest to the further development of high-capacity Si-based anode in Li-ion batteries.

Investigations of the processing–structure–performance relationships of an additively manufactured AlSi10Mg alloy via directed energy deposition

In this paper, the microstructure formation mechanism of an AlSi10Mg alloy prepared by laser directed energy deposition (DED-LB) and its influence on the mechanical properties was fully studied. The relationships between the microstructure characteristic scale, the molten pool solidification/thermal cycle conditions, and the tensile mechanical properties were established by combining the numerical simulation, theoretical calculation, and experimental validation. The as-deposited microstructure consists of the columnar α-Al dendritic array growing epitaxially along the building direction with the primary dendritic arm spacing of 18 ± 4.5 µm, the dendritic arm cell of 3 ± 1 µm surrounded by the refined eutectic network, and the Si precipitation of 17.7 ± 0.8 nm dispersed in the α-Al dendritic trunk. The feature size of the primary dendritic arm spacing and the dendritic arm cell size can be well predicted using the Kurz-Fisher and KGT dendritic growth models. The formation and size evolution of the Si precipitation was well described by the non-isothermal aging KWN model for the first time. The as-DED-LB-processed AlSi10Mg alloy exhibits a good comprehensive mechanical property with a yield strength of 187 ± 1.5 MPa and elongation to fracture of 7.4 ± 0.5%. The boundary strengthening from the eutectic phase network, the load-bearing capacity for dislocations caused by refined dendritic arms, and the precipitation strengthening of nano-Si particles play a major role in the improvement of the tensile strength and hardening ability. As a result, a quantitative relationship of the processing–microstructure–performance has been systematically investigated and established, which explores a method for the precision control and large-scale application of DED-AlSi10Mg alloys.

Si@nitrogen-doped porous carbon derived from covalent organic framework for enhanced Li-storage

Due to ultra-high theoretical capacity (4200 mAh g−1), silicon (Si) is an excellent candidate for the anode of lithium-ion batteries (LIBs). However, the application of Si is severely limited by its volume expansion of approximately 300% during the charge/discharge process. Herein, nitrogen-doped porous carbon (NC) capped nano-Si particles (Si@NC) composites with a core-shell structure were obtained by calcination of covalent organic frameworks (COFs) encapsulated nano-Si. COFs is a crystalline material with well-ordered structures, adjustable and ordered pores and abundant N atoms. After carbonization, the well-ordered pores and frameworks were kept well. Compared with other Si@NC composites, the well-ordered NC framework shell derived from COFs possesses high elasticity and well-ordered pores, which provides space for the volume expansion of nano-Si, and a channel to transfer Li+. The core-shell Si@NC composite exhibited good performances when applied as the anode of LIBs. At a current density of 100 mA g−1, it exhibited a discharge-specific capacity of 1534.8 mAh g−1 after 100 cycles with a first-coulomb efficiency of 69.7%. The combination of COFs with nano-Si is a better strategy for the preparation of anode materials of LIBs.

Self-assembled three-dimensional Si/carbon frameworks as promising lithium-ion battery anode

Silicon, the most prospecting anode material for lithium batteries, has been receiving enormous attention, but silicon-based composite materials exhibit severe problems of structural instability and insufficient electron/ion conductivity, which is a major bottleneck limiting its practical applications. Herein, a three-dimensional (3D) silicon/carbon framework, CHSP, is designed to solve this problem. The nano-Si particles are well fixed by the interconnected porous conducting network, which not only enhances the ion/electron transport, but also buffers the volume change of Si effectively. As a result, the CHSP exhibits satisfying rate performance and a reversible capacity of as high as 1332 mA h g−1 at 1000 mA g−1 for 200 cycles. This research provides a practical approach to improve silicon anode performance in aspects of cycling stability and facile 3D structures synthesis process.

Improving Yield Components and Desirable Eating Quality of Two Wheat Genotypes Using Si and NanoSi Particles under Heat Stress.

Global climate change is a significant challenge that will significantly lower crop yield and staple grain quality. The present investigation was conducted to assess the effects of the foliar application of either Si (1.5 mM) or Si nanoparticles (1.66 mM) on the yield and grain quality attributes of two wheat genotypes (Triticum aestivum L.), cv. Shandweel 1 and cv. Gemmeiza 9, planted at normal sowing date and late sowing date (heat stress). Si and Si nanoparticles markedly mitigated the observed decline in yield and reduced the heat stress intensity index value at late sowing dates, and improved yield quality via the decreased level of protein, particularly glutenin, as well as the lowered activity of α-amylase in wheat grains, which is considered a step in improving grain quality. Moreover, Si and nanoSi significantly increased the oil absorption capacity (OAC) of the flour of stressed wheat grains. In addition, both silicon and nanosilicon provoked an increase in cellulose, pectin, total phenols, flavonoid, oxalic acid, total antioxidant power, starch and soluble protein contents, as well as Ca and K levels, in heat-stressed wheat straw, concomitant with a decrease in lignin and phytic acid contents. In conclusion, the pronounced positive effects associated with improving yield quantity and quality were observed in stressed Si-treated wheat compared with Si nanoparticle-treated ones, particularly in cv. Gemmeiza 9.

Characterization of nanostructures in a high pressure die cast Al-Si-Cu alloy

Several interesting nanostructures of high pressure die cast commercial Al-Si-Cu alloy (A383) were characterized via transmission electron microscopy (TEM) and atom probe tomography (APT). The refinement of the eutectic Si, which was caused by Sr addition, was found to be associated with the formation of nano-Al particles (∼5 nm), with Cu partitioning (up to 5 at.%) at the Al/Si interface, within the eutectic Si. Direct observation of Sr segregation (0.4 at.%) at the interface between the eutectic Al and refined eutectic Si was achieved using APT. It is proposed that Sr refines the eutectic Si by restricting the growth of Si. Interestingly, the segregation of Mg (10.2 at.%) and Cu (0.9 at.%) is also present at the interface between the eutectic Al and the refined eutectic Si. Moreover, the presence of nano-Si particles (∼20 nm) in the primary Al was characterized in the primary Al via APT. Segregations of Mg (2.9 at.%) and Cu (2.8 at.%) were also found at the interface between the primary Al and the nano-Si particles. Density functional theory (DFT) was used to assess the driving force for the segregation behavior of Cu and Mg at the Al/Si interface. DFT results also suggest that the segregation of Cu and Mg slightly decreases the cohesive energy of Al/Si interface but is a function of the length scale of the interface.

Simultaneously minimizing residual stress and enhancing strength of selective laser melted nano-TiB2 decorated Al alloy via post-uphill quenching and ageing

Selective laser melting (SLM) of aluminium alloys is of research interest to produce customized or complex-shaped metal components for functional or structural applications. In order to palliate the undesirable residual stress developed in the SLM process, traditional post-annealing heat treatment has been widely used to lower residual stress in selective laser melted (SLMed) Al alloys. However, the traditional post-annealing method usually leads to a decrease in strength which is another concern for applications. In this study, we developed and validated a new strategy combining post-uphill quenching and subsequent ageing to simultaneously minimise residual stress and increase the strength of SLMed nano-TiB2 decorated Al alloy parts. The results show that the high as-built residual stress was partly counteracted by the newly-produced residual stress in the opposite direction during the uphill quenching stage and synergistically reduced by dislocation recovery during the ageing stage. The microstructural features of grains and cell structures remain unchanged after the treatment. While substantial new nano-Si particles with dot-like or needle-like morphology precipitate inside the cells. The tensile strength was improved mainly due to effective precipitation strengthening by dispersed nanosized Si precipitates. The proposed strategy is expected to be useful in other materials and components fabricated by SLM in which residual stress is also unwanted.

Optically Controlled Supercapacitors: Functional Active Carbon Electrodes with Semiconductor Particles.

Supercapacitors, S-C—capacitors that take advantage of the large capacitance at the interface between an electrode and an electrolyte—have found many short-term energy applications. The parallel plate cells were made of two transparent electrodes (ITO), each covered with a semiconductor-embedded, active carbon (A-C) layer. While A-C appears black, it is not an ideal blackbody absorber that absorbs all spectral light indiscriminately. In addition to a relatively flat optical absorption background, A-C exhibits two distinct absorption bands: in the near-infrared (near-IR and in the blue. The first may be attributed to absorption by the OH− group and the latter, by scattering, possibly through surface plasmons at the pore/electrolyte interface. Here, optical and thermal effects of sub-μm SiC particles that are embedded in A-C electrodes, are presented. Similar to nano-Si particles, SiC exhibits blue band absorption, but it is less likely to oxidize. Using Charge-Discharge (CD) experiments, the relative optically related capacitance increase may be as large as ~34% (68% when the illuminated area is taken into account). Capacitance increase was noted as the illuminated samples became hotter. This thermal effect amounts to <20% of the overall relative capacitance change using CD experiments. The thermal effect was quite large when the SiC particles were replaced by CdSe/ZnS quantum dots; for the latter, the thermal effect was 35% compared to 10% for the optical effect. When analyzing the optical effect one may consider two processes: ionization of the semiconductor particles and charge displacement under the cell’s terminals—a dipole effect. A model suggests that the capacitance increase is related to an optically induced dipole effect.

Good Structural Stability of Si Anodes Achieved through Dispersant Addition and Use of Carbon Fabric as Conductive Framework

Carbon fabric is proposed as the electrode support instead of Cu foil as the current collector in the fabrication of Si-anode, in order to prevent electrode pulverization during cell charge/discharge. Polyvinylpyrrolidone is used as a suitable dispersant to improve the anode slurry’s compatibility with the carbon fabric and final uniform distribution of the anode materials. The anode with added dispersant exhibits a lower resistance, and the constructed cell presents a higher capacity than that without dispersant in the anode (3561 vs 2755 mAh g−1) in the first charge/discharge cycle under a current of 420 mA g−1. After charge/discharge for 150 cycles, the stress from repeated formation/deformation of the solid-electrolyte interface layer only breaks a part of the fibers in the carbon fabric, while acceptable structural integrity is maintained in the anode. Interestingly, the added dispersant enhances both the uniform distribution of nano-Si electrode materials and the anode’s conductivity, while diminishing the fabric damage during charge/discharge cycles. This is attributed to the smaller, well-deagglomerated nano-Si particles that are better at sustaining the stress caused by cell charge/discharge, and also the binding force from the dispersant to reinforce the carbon fabric.

Silicon Microreactor as a Fast Charge, Long Cycle Life Anode with High Initial Coulombic Efficiency Synthesized via a Scalable Method

Applications of silicon as a high-performance anode material have been impeded by its low intrinsic conductivity and huge volume expansion (>300%) during lithiation. To address these problems, nano-Si particles along with conductive coatings and engineered voids are often employed, but this results in high-cost anodes. Here, we report a scalable synthesis method that can realize high specific capacity (∼800 mAh g–1), ultrafast charge/discharge (at 8 A g–1 Si), and high initial Coulombic efficiency (∼90%) with long cycle life (1000 cycles) at the same time. To achieve 1000 cycle stability, micron-sized Si particles are subjected to high-energy ball milling to create nanostructured Si building blocks with nano-channel-shaped voids encapsulated inside a nitrogen (N)-doped carbon shell (termed as Si microreactor). The nanochannel voids inside a Si microreactor not only offer the space to accommodate the volume expansion of Si but also provide fast pathways for Li-ion diffusion into the center of the nanostructured Si core and thus ultrafast charge/discharge capability. The porous N-doped carbon shell helps to improve the conductivity while allowing fast Li-ion transport and confining the volume expansion within the Si microreactor. Submicron-sized Si microreactors with a limited specific surface area (35 m2 g–1) afford sufficient electrode/electrolyte interfacial area for fast lithiation/delithiation, leading to the specific capacity ranging from ∼800 to 420 mAh g–1 under ultrafast charging conditions (8 A g–1), but not too much interfacial area for surface side reactions and thus high initial Coulombic efficiency (∼90%). Since Si microreactors with superior electrochemical properties are synthesized via an industrially scalable and eco-friendly method, they have the potential for practical applications in the future.

Enhancement of ZIF-8 derived N-doped carbon/silicon composites for anode in lithium ions batteries

It is urgent to develop novel anode materials with high energy density and facile synthetic procedures, since the development of commercial lithium ions batteries (LIBs) is limited by the unsatisfied capacity of graphite. Herein, we propose a modified method to prepare core-shell structured ZIF-8 derived N-doped carbon/silicon (Si@NC) composites (6.6 wt% of nano-Si), featuring facile synthetic procedures and mild condition. The physicochemical properties of the ZIF-8 derived N-doped carbon are not changed when the nano-Si particles are employed as the seeds. The Si@NC composites deliver high reversible capacity of 724 mAh g−1. Attributed to the good charge conductivity and structural stability of the ZIF-8 derived N-doped carbon, the Si@NC composites exhibit good rate performance (98.5% of the initial average capacity is retained after being cycled at different current density) and cycle stability (302 mAh g−1 while that of commercial graphite is ~10 mAh g−1 at 1000 mA g−1 after 800 cycles). The enhancement of lithium storage capability of the ZIF-8 derived N-doped carbon shows promising application in high energy density LIBs.

Characterization of Nanostructures in the High Pressure Die Cast A383 Alloys

Several interesting nanostructures of high pressure die cast A383 alloys were characterized via transmission electron microscopy (TEM) and atom probe tomography (APT). The refinement of the eutectic Si, which was caused by Sr addition, was found to be associated with the formation of nano-Al particles (~5 nm), with Cu partitioning (up to 5 at. %) at the Al/Si interface, within the eutectic Si. Direct observation of Sr segregation (0.4 at. %) was achieved at the interface between the eutectic Al and refined eutectic Si using APT. It is proposed that Sr refines the eutectic Si by restricting the growth of Si. Interestingly, the segregation of Mg (10.2 at. %) and Cu (0.9 at. %) is also present at the interface between the eutectic Al and the refined eutectic Si. Moreover, the presence of nano-Si particles (~20 nm) in the primary Al was characterized in the primary Al via APT. Segregations of Mg (2.9 at. %) and Cu (2.8 at. %) were also found at the interface between the primary Al and the nano-Si particles. Density functional theory (DFT) was used to assess the driving force for the segregation behavior of Cu and Mg at the Al/Si interface. DFT results also suggest that the segregation of Cu and Mg slightly decreases the cohesive energy of Al/Si interface but is a function of the length scale of the interface.

High Performance Lithium Silicide Electrode Enable By Molecular Layer Deposition

The energy demand of our society is increasing without precedents. Lithium-Ion Batteries (LIBs) are and have been an enabler of the present communication revolution; LIBs are the powerhouse of portable communication devices. Consumers are starting to demand more sustainable and more environmentally friendly energy sources, energy production and distribution. To satisfy these demands, the next generation of rechargeable batteries will need higher specific energy and power (per mass) and energy and power density (per volume) than the current generation of LIBs. The current technology uses Lithium Metal Oxide (LMO) as positive electrodes and graphite as a negative electrode. This system has an energy density value ca. 250 WhL-1. To improve the power and energy density of the LIBs devices; new electrode material needs to be developed.Silicon (Si) has become one of the most investigated materials for LIB negative electrodes because of its ability to accommodate 3.75 moles of Li per mole of Si (Li15Si4), leading to a theoretical capacity of 3,579 mA h/g at room temperature1. While 372 mA h/g is the theoretical capacity for graphite2, this material can only accommodate 1 mole of Li per 6 mol of C.Despite Si advantages, progress towards a commercially available Si negative electrode has been impeded by their rapid capacity fade, poor rate capability, and low coulombic efficiency. The cause of electrode degradation is the Si volume change of ~300% upon lithium insertion and extraction3, presenting a major problem for electrochemical performance. The volume fluctuation damages the electrical contact between Si and the current collector, being too large to be controlled by currently developed coating technologies.One of the leading strategies established for the realization of such an approach is coating nano-Si particles with flexible materials to attempt to accommodate the volumetric changes of the particles. In this context, we propose to carry out a surface modification, in which Molecular Layer Deposition (MLD) is utilized to grow a mechanically robust, flexible coating, to undertake the Si expansion and contraction. For it, we have used TiCl4 molecule and as it is a relatively small molecule, when combined with the larger organic reactants, has high growth rates that are mainly limited by steric hindrance caused by the organic reactants. For these reasons, the recipe here developed is based on Glycerol and TiCl4 as the titanium precursor.The composition of the films was studied using Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope-Energy-dispersive X-ray spectroscopy (SEM-EDX). Multiple characteristic absorption modes for both carbon and titanium related groups can be observed in the FTIR spectrum (Figure 1). These techniques confirm that the combination of both the carbon-related groups and the Ti absorptions providing evidence for the successful deposition of a hybrid organic-inorganic film showing that we are able to detect Ti in the surface of the electrode.Cyclic Voltammetry was used to characterize the electrochemical performance of the LixSi negative electrode coated with titanicone. We have successfully shown the deposition of titanicone on LixSi electrode and an initial electrochemical assessment of this electrode. These electrodes exhibit high capacity, around 2,000 mAhg-1 at 0.10C, and 270 mAhg-1 at 20C corroborating the goodness of the proposed methodology.Typical voltammogram shows the formation of the solid electrolyte interface, evident in the first cycle. In the subsequent scans, these peaks disappear (Figure 2). The sample exhibit the regular waves are corresponding to the Si redox reaction. Prosini PP, Cento C, Rufoloni A, Rondino F, Santoni A. A lithium-ion battery based on LiFePO4 and silicon nanowires. . 2015;269:93-97.Ikonen T, Nissinen T, Pohjalainen E, Sorsa O, Kallio T, Lehto VP. Electrochemically anodized porous silicon: Towards simple and affordable anode material for li-ion batteries. . 2017;7(1):7880.Zhao J, Lu Z, Liu N, Lee H, McDowell MT, Cui Y. Dry-air-stable lithium silicide and lithium oxide shell nanoparticles as high-capacity prelithiation reagents. . 2014;5:5088. Figure 1

Influence of Different Diss Fiber Treatments over the Properties of Poly Propylene/Recycled and Regenerated Low Density Polyethylene Based Biocomposites

This study aims the valorization of diss fibers for the production of biocomposites based on blends of recycled and regenerated low density polyethylene (rLDPE) and polypropylene (PP). Thus, the study of different diss fibers treatments was carried out to achieve the best performance of the final biocomposites. The polymeric blends were prepared by using PP/rLDPE (75/25) matrix and adding nano Si particles as reinforcement and maleic anhydride functionalized ethylene copolymer rubber/SiO2 (MAC/SiO2) as compatibilizer. Based on this formulation, different biocomposites were prepared by introducing untreated (UDF), thermally treated (TTDF) and chemically treated (CTDF) diss fibers. Several techniques were used for the characterization of the diss fibers and the final biocomposites. The effect of the fiber treatments was assessed by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). On the other side, the biocomposites were tested for different parameters such as mechanical properties (tensile test) and thermal stability (thermogravimetric analysis and differential scanning calorimetry). Besides other techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized to determine the morphology of the materials. The final results showed an improvement of the mechanical properties and a satisfactory interfacial adhesion after the introduction of the treated diss fiber into the polymeric matrix, especially in the case of the thermally treated ones. Furthermore, thermal stability was not compromised after the addition of the fibers.

Si@Cu3Si nano-composite prepared by facile method as high-performance anode for lithium-ion batteries

Due to the high density of lithium storage and abundant mineral resources, silicon has been well accepted as a promising anode for the new-generation lithium-ion batteries. In recent years, its poor cycle stability due to drastically volumetric change has been remarkably improved by means of such composites as Si–Cu or Si–Cu3Si. However, the preparation is still complicated. The present work proposed an environmentally friendly and facile method, that is, implementing hydrogenation reduction and subsequent calcinations on the nano Si particles immersed in CuCl2 solution to obtain the Si–Cu3Si composite (denoted as Si@Cu3Si) with coherent phase boundaries. This architecture helps reduce the contact between Si and electrolyte, depressing the formation of SEI film and the cyclic deterioration of discharge capacity. It not only enhances the cyclic stability by preserving the capacity of 1000 mAhg−1 for 300 cycles, but also improves the rate capability and kinetics of the electrode. Based on detections by X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the effects of morphology, composition and structure on the electrochemical performance of the nano-sized Si@Cu3Si anode was clarified in the present work.

Multi-step low-cost synthesis of ultrafine silicon porous structures for high-reversible lithium-ion battery anodes

We demonstrate multi-step synthesis of silicon porous structures with various particle sizes via low-cost annealing and pickling reactions from ball-milled Mg2Si or Si/Mg powder. Thereinto, the ultrafine Si porous structures (< 50 nm) have been prepared by the two-step alloying/de-alloying processes between Si and Mg, and the formation processes and reaction mechanism have been discussed as well. When used as an anode material for lithium-ion batteries, the porous Si anode with finer particle size shows better capacity retention and coulombic efficiency, confirming the particle size has a great impact on cycling performance. Moreover, the ultrafine porous Si anodes without any buffer medium demonstrate a reversible discharge capacity of ~ 800 mAhg−1 after 1000 long cycles at 1 Ag−1, which is extremely better than the commercial nano-Si particles and graphite anodes. It is believed that the good electrochemical performance could be attributed to the uniform porous structure and superfine particle size that can alleviate the volume change significantly. Hence, these low-cost and simple scalable methods have provided useful strategies for the industrialization of Si anode materials.