Silicon core-mesoporous shell carbon spheres as high stability lithium-ion battery anode

Fabrication of silicon-based nickel nanoflower-encapsulated gelatin microspheres as an active antimicrobial carrier

Local antibiotic application might mitigate the burgeoning problem of rapid emergence of antibiotic resistance in pathogenic microbes. To accomplish this, delivery systems must be engineered. Hydrogels have a wide range of physicochemical properties and can mimic the extracellular matrix, rendering them promising materials for local antibacterial agent application. Here, we synthesized antibacterial silicon (Si)-based nickel (Ni) nanoflowers (Si@Ni) and encapsulated them in gelatin methacryloyl (GelMA) using microfluidic and photo-crosslink technology, constructing uniform micro-sized hydrogel spheres (Si@Ni-GelMA). Si@Ni and Si@Ni-GelMA were characterized using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Injectable Si@Ni-GelMA exhibited excellent antibacterial activities owing to the antibiotic effect of Ni against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus, while showing negligible cytotoxicity. Therefore, the Si@Ni-GelMA system can be used as drug carriers owing to their injectability, visible light-mediated crosslinking, degradation, biosafety, and superior antibacterial properties.

Stress-Relief Engineering in a N-Doped C-Modified Hierarchical Nanoporous Si Anode with a Microcurved Pore Wall Structure for Enhanced Lithium Storage

The commercialization of alloy-type anodes has been hindered by rapid capacity degradation due to volume fluctuations. To address this issue, stress-relief engineering is proposed for Si anodes that combines hierarchical nanoporous structures and modified layers, inspired by the phenomenon in which structures with continuous changes in curvature can reduce stress concentration. The N-doped C-modified hierarchical nanoporous Si anode with a microcurved pore wall (N-C@m-HNP Si) is prepared from inexpensive Mg-55Si alloys using a simple chemical etching and heat treatment process. When used as the anode for lithium-ion batteries, the N-C@m-HNP Si anode exhibits initial charge/discharge specific capacities of 1092.93 and 2636.32 mAh g-1 at 0.1 C (1 C = 3579 mA g-1), respectively, and a stable reversible specific capacity of 1071.84 mAh g-1 after 200 cycles. The synergy of the hierarchical porous structure with a microcurved pore wall and the N-doped C-modified layer effectively improves the electrochemical performance of N-C@m-HNP Si, and the effectiveness of stress-relief engineering is quantitatively analyzed through the theory of elastic bending of thin plates. Moreover, the formation process of Li15Si4 crystals, which causes substantial mechanical stress, is investigated using first-principles molecular dynamic simulations to reveal their tendency to occur at different scales. The results demonstrate that the hierarchical nanoporous structure helps to inhibit the transformation of amorphous LixSi into metastable Li15Si4 crystals during lithiation.

Cu and Ni Co-Doped Porous Si Nanowire Networks as High-Performance Anode Materials for Lithium-Ion Batteries

Due to its extremely high theoretical mass specific capacity, silicon is considered to be the most promising anode material for lithium-ion batteries (LIBs). However, serious volume expansion and poor conductivity limit its commercial application. Herein, dealloying treatments of spray dryed Al-Si-Cu-Ni particles are performed to obtain a Cu/Ni co-doped Si-based anode material with a porous nanowire network structure. The porous structure enables the material to adapt to the volume changes in the cycle process. Moreover, the density functional theory (DFT) calculations show that the co-doping of Cu and Ni can improve the capture ability towards Li, which can accelerate the electron migration rate of the material. Based on the above advantages, the as-prepared material presents excellent electrochemical performance, delivering a reversible capacity of 1092.4 mAh g-1 after 100 cycles at 100 mA g-1. Even after 500 cycles, it still retains 818.7 mAh g-1 at 500 mA g-1. This study is expected to provide ideas for the preparation and optimization of Si-based anodes with good electrochemical performance.

Preparation of Buffered Nano-Submicron Hierarchical Structure Hollow SiOx @C Anodes for Lithium-Ion Battery Materials with Carboxymethyl Chitosan

Silicon-based materials are among the most promising anode materials for next-generation lithium-ion batteries. However, the volume expansion and poor conductivity of silicon-based materials during the charge and discharge process seriously hinder their practical application in the field of anodes. Here, we choose carboxymethyl chitosan (CMCS) as the carbon source coating and binding on the surface of nano silicon and hollow silicon dioxide (H-SiO2 ) to form a hierarchical buffered structure of nano-hollow SiOx @C. The hollow H-SiO2 can alleviate the volume expansion of nano silicon during the lithiation process under continuous cycling. Meanwhile, the carbon layer carbonized by CMCS containing N-doping further regulates the silicon's expansion and improves the conductivity of the active materials. The as- prepared SiOx @C material exhibits an initial discharge capacity of 985.4 mAh g-1 with the decay rate of 0.27 % per cycle in 150 cycles under the current density of 0.2 A g-1 . It is proved that the hierarchical buffer structure nano-hollow SiOx @C anode material has practical application potential.

Improving Electrochemical Performance of Thick Silicon Film Anodes with Implanted Solid Lithium Source Electrolyte

Silicon is a potential next-generation anode material for a lithium-ion battery. However, the large-scale application of silicon is restricted by poor electrical conductivity, large volume change, and high irreversible capacity during the charge/discharge process. Here, we proposed a simple strategy by preimplanting a solid lithium source electrolyte (Li₂CO₃ and Li₂O) into Si thick film to improve the electrochemical properties of Si materials. The implanted solid lithium source electrolyte participates in and induces the formation of SEI not only on the top surface of Si film but also in the interface of Si particles. The thick Si film with the implanted solid lithium electrolyte (a thickness of ∼10 μm) delivers above 2000 mAh g^-1 specific capacity, >92% initial Coulombic efficiency, and ∼87% capacity retention over 150 cycles at 400 mA g^-1. The present work sheds light on the design of high capacity and long cycle life electrode materials for other batteries.

Injectable hyaluronic acid hydrogel encapsulated with Si-based NiO nanoflower by visible light cross-linking: Its antibacterial applications

Bacterial infections have become a severe threat to human health and antibiotics have been developed to treat them. However, extensive use of antibiotics has led to multidrug-resistant bacteria and reduction of their therapeutic effects. An efficient solution may be localized application of antibiotics using a drug delivery system. For clinical application, they need to be biodegradable and should offer a prolonged antibacterial effect. In this study, a new injectable and visible-light-crosslinked hyaluronic acid (HA) hydrogel loaded with silicon (Si)-based nickel oxide (NiO) nanoflowers (Si@NiO) as an antibacterial scaffold was developed. Si@NiO nanoflowers were synthesized using chemical bath deposition before encapsulating them in the HA hydrogel under a mild visible-light-crosslinking conditions to generate a Si@NiO-hydrogel. Si@NiO synthesis was confirmed using scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. As-prepared Si@NiO-hydrogel exhibited enhanced mechanical properties compared to a control bare hydrogel sample. Moreover, Si@NiO-hydrogel exhibits excellent antibacterial properties against three bacterial strains (P. aeruginosa, K. pneumoniae, and methicillin-resistant Staphylococcus aureus (>99.9% bactericidal rate)) and negligible cytotoxicity toward mouse embryonic fibroblasts. Therefore, Si@NiO-hydrogel has the potential for use in tissue engineering and biomedical applications owing to its injectability, visible-light crosslink ability, degradability, biosafety, and superior antibacterial property.

One-Dimensional Nanoscale Si/Co Based on Layered Double Hydroxides towards Electrochemical Supercapacitor Electrodes

It is well known that layered double hydroxides (LDHs) are two-dimensional (2D) layered compounds. However, we modified these 2D layered compounds to become one-dimensional (1D) nanostructures destined for high-performance supercapacitors applications. In this direction, silicon was inserted inside the nanolayers of Co-LDHs producing nanofibers of Si/Co LDHs through the intercalation of cyanate anions as pillars for building nanolayered structures. Additionally, nanoparticles were observed by controlling the preparation conditions and the silicon percentage. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermal analyses have been used to characterize the nanolayered structures of Si/Co LDHs. The electrochemical characterization was performed by cyclic voltammetry and galvanic charge–discharge technique in 2M KOH electrolyte solution using three-electrode cell system. The calculated specific capacitance results indicated that the change of morphology from nanoparticles or plates to nanofibers had a positive effect for improving the performance of specific capacitance of Si/Co LDHs. The specific capacitance enhanced to be 621.5 F g−1 in the case of the nanofiber of Si/Co LDHs. Similarly, the excellent cyclic stability (84.5%) was observed for the nanofiber. These results were explained through the attribute of the nanofibrous morphology and synergistic effects between the electric double layer capacitive character of the silicon and the pseudo capacitance nature of the cobalt. The high capacitance of ternary Si/Co/cyanate LDHs nanocomposites was suggested to be used as active electrode materials for high-performance supercapacitors applications.

Dual carbon and void space confined SiOx/C@void@Si/C yolk-shell nanospheres with high-rate performances and outstanding cyclability for lithium-ion batteries anodes

Silicon-based anode materials with high theoretical capacity have great challenges of enormous volume expansion and poor electronic conductivity. Herein, a novel dual carbon confined SiO_x/C@void@Si/C yolk-shell monodisperse nanosphere with void space have been fabricated through hydrothermal reaction, carbonization, and in-situ low-temperature aluminothermic reduction. Furthermore, the O/Si ratio and void space between SiO_x/C core and Si/C shell can be effectively tuned by the length of aluminothermic reduction time. The SiO_x/C core plays a role of maintaining the spherical structure and the void space can accommodate the volume expansion of Si. Moreover, the inner and outer carbons not only alleviate volume variation of SiO_x and Si but also enhance the electrical conductivity of composites. Benefiting from the synergy of the double carbon and void space, the optimized VSC-14 anode affords prominent cycle stability with reversible capacity of 1094 mAh g^-1 after 550 cycles at 200 mA g^-1. By pre-lithiation treatment, the VSC-14 achieves an initial Coulombic efficiency of 93.27% at 200 mA g^-1 and a reversible capacity of 348 mAh g^-1 at 5 A g^-1 after 4000 cycles. Furthermore, the pouch cell using VSC-14 anode and LiFePO₄ cathode delivers a reversible capacity of 138 mAh g^-1 at 0.2C. We hope this strategy can provide a scientific method to synthesis yolk-shell Si-based materials.

UV-ozone contributions towards facile self-assembly and high performance of silicon-carbon fiber materials as lithium-ion battery anodes

Si-carbon composites have been considered as next generation lithium-ion battery anodes, with a view to sufficiently exerting the respective superiorities of high specific capacity of Si as well as excellent mechanical flexibility and electrical conductivity of carbon. However, direct blending of carbon with Si cannot obtain a synergy composite, resulting in inferior cycle properties during charge-discharge due to huge volume changes and deficient electron-conducting channels from the unavoidably aggregated Si. Herein, the composition of carbon fibers (CNFs) with Si nanoparticles (SiNPs) has been performed through UV-ozone surface modification followed by electrostatic self-assembly. It is found that solvent-free UV-ozone exposure of CNFs for 20 min successfully introduces carboxylic groups, as conventional acid treatment for 12 h. Besides UV-ozone surface modification provides an efficient and scalable route, the distribution and functionalization of CNFs can be also modified to effectively combine with amino-functionalized SiNPs. As a result, such Si-CNF composites containing 70.0 wt% SiNPs are able to exhibit excellent cycle performance with high coulombic efficiency of 74.8% at the 1st cycle and high specific discharge capacity of 1063 mAh g^-1 at the 400th cycle.

The Latest Trends in Electric Vehicles Batteries

Global energy demand is rapidly increasing due to population and economic growth, especially in large emerging countries, which will account for 90% of energy demand growth to 2035. Electric vehicles (EVs) play a paramount role in the electrification revolution towards the reduction of the carbon footprint. Here, we review all the major trends in Li-ion batteries technologies used in EVs. We conclude that only five types of cathodes are used and that most of the EV companies use Nickel Manganese Cobalt oxide (NMC). Most of the Li-ion batteries anodes are graphite-based. Positive and negative electrodes are reviewed in detail as well as future trends such as the effort to reduce the Cobalt content. The electrolyte is a liquid/gel flammable solvent usually containing a LiFeP6 salt. The electrolyte makes the battery and battery pack unsafe, which drives the research and development to replace the flammable liquid by a solid electrolyte.

A surface-engineering-assisted method to synthesize recycled silicon-based anodes with a uniform carbon shell-protective layer for lithium-ion batteries

Yolk-shell silicon/carbon composite encapsulated by uniform carbon shell (Si@C) are becoming an effective method to mitigate volume-related issues of Si-based anodes and maintain an excellent performance for lithium-ion batteries (LIBs). However, a uniform carbon shell in Si@C is difficult to guarantee. Herein, a facile surface-engineering-assisted strategy is described to prepare Si@C composite with low-cost modified recycled waste silicon powders (RWSi) as core coated by a uniform carbon shell-protective layer derived from the pyrolysis of poly (methyl methacrylate) (PMMA) as carbon source (m-RWSi@PMMA-C). In this process, surface-engineering is performed with silane coupling agent kh550 to functionalize the RWSi particles via a silanization reaction, guaranteeing a uniform PMMA coating which will be transformed into carbon shell-protective layer after carbonization. The m-RWSi@PMMA-C electrode delivers an optimal discharge capacity of 1083 mAhg^-1 at 200 mAg^-1 after 200 cycles with an initial capacity of 3176.2 mAhg^-1 and a high initial Coulombic efficiency (ICE) of 75.6%. Based on these results, the recycled silicon-based anode with a uniform carbon shell-protective layer displays great application potential and it also brings a new perspective on silicon-based anodes via surface-engineering method for LIBs.

Recent Advances in Silicon-Based Electrodes: From Fundamental Research toward Practical Applications

The increasing demand for higher-energy-density batteries driven by advancements in electric vehicles, hybrid electric vehicles, and portable electronic devices necessitates the development of alternative anode materials with a specific capacity beyond that of traditional graphite anodes. Here, the state-of-the-art developments made in the rational design of Si-based electrodes and their progression toward practical application are presented. First, a comprehensive overview of fundamental electrochemistry and selected critical challenges is given, including their large volume expansion, unstable solid electrolyte interface (SEI) growth, low initial Coulombic efficiency, low areal capacity, and safety issues. Second, the principles of potential solutions including nanoarchitectured construction, surface/interface engineering, novel binder and electrolyte design, and designing the whole electrode for stability are discussed in detail. Third, applications for Si-based anodes beyond LIBs are highlighted, specifically noting their promise in configurations of Li-S batteries and all-solid-state batteries. Fourth, the electrochemical reaction process, structural evolution, and degradation mechanisms are systematically investigated by advanced in situ and operando characterizations. Finally, the future trends and perspectives with an emphasis on commercialization of Si-based electrodes are provided. Si-based anode materials will be key in helping keep up with the demands for higher energy density in the coming decades.

Improving electrochemical performances of Lithium-rich oxide by cooperatively doping Cr and coating Li3PO4 as cathode material for Lithium-ion batteries

Lithium-rich layered oxides exhibit one of the highest reversible discharge capacities among cathode materials for lithium-ion batteries. However, their voltage decay and poor cycle stability severely restrict their use as a commercial cathode material. In this work, a novel approach of that combines Cr doping and a Li₃PO₄ coating was designed to address the problems associated with lithium-rich Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ materials. The synergistic method not only increases the discharge capacity and cycle stability but also decreases the voltage decay. The 1.0 wt% Li₃PO₄ coating and 0.08 Cr doping on Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode shows a capacity retention of 76.5% compared to the 59.0% capacity retention for the pristine electrode after 200 cycles. The initial discharge capacity is also increased from 255.8 mAh·g^-1 to 265.2 mAh·g^-1. In addition, the discharge voltage decay decreases from 0.84 V to 0.39 V after 200 cycles as a result of the Cr doping and Li₃PO₄ coating. These enhanced electrochemical properties are attributed to the fact that the Cr doping stabilized the layered structure and inhibited its phase transformation to the spinel phase, and the Li₃PO₄ coating confined the interfacial side reactions between the electrode and electrolyte. This work may provide a new method to solve the subsistent problems of lithium-rich cathode materials.

Surface Oxidation of Nano-Silicon as a Method for Cycle Life Enhancement of Li-ion Active Materials

Among the many studied Li-ion active materials, silicon presents the highest specific capacity, however it suffers from a great volume change during lithiation. In this work, we present two methods for the chemical modification of silicon nanoparticles. Both methods change the materials' electrochemical characteristics. The combined XPS and SEM results show that the properties of the generated silicon oxide layer depend on the modification procedure employed. Electrochemical characterization reveals that the formed oxide layers show different susceptibility to electro-reduction during the first lithiation. The single step oxidation procedure resulted in a thin and very stable oxide that acts as an artificial SEI layer during electrode operation. The removal of the native oxide prior to further reactions resulted in a very thick oxide layer formation. The created oxide layers (both thin and thick) greatly suppress the effect of silicon volume changes, which significantly reduces electrode degradation during cycling. Both modification techniques are relatively straightforward and scalable to an industrial level. The proposed modified materials reveal great applicability prospects in next generation Li-ion batteries due to their high specific capacity and remarkable cycling stability.

Silicon-nanoparticle-based composites for advanced lithium-ion battery anodes

Lithium-ion batteries (LIBs) play an important role in modern society. The low capacity of graphite cannot meet the demands of LIBs calling for high power and energy densities. Silicon (Si) is one of the most promising materials instead of graphite, because of its high theoretical capacity, low discharge voltage, low cost, etc. However, Si shows low conductivity of both ions and electrons and exhibits a severe volume change during cycles. Fabricating nano-sized Si and Si-based composites is an effective method to enhance the electrochemical performance of LIB anodes. Using a small size of Si nanoparticles (SiNPs) is likely to avoid the cracking of this material. One critical issue is to disclose different types and electrochemical effects of various coupled materials in the Si-based composites for anode fabrication and optimization. Hence, this paper reviews diverse SiNP-based composites for advanced LIBs from the perspective of composition and electrochemical effects. Almost all kinds of materials that have been coupled with SiNPs for LIB applications are summarized, along with their electrochemical influences on the composites. The integrated materials, including carbon materials, metals, metal oxides, polymers, Si-based materials, transition metal nitrides, carbides, dichalcogenides, alloys, and metal-organic frameworks (MOFs), are comprehensively presented.

Interaction and Kinetics Study of the Co-Gasification of High-solid Anaerobic Digestate and Lignite

This study aims at investigating the interaction and kinetics behavior of the co-gasification of digestate and lignite. The co-pyrolysis performances of digestate and lignite blended by dry process were better than that blended by wet process, while the wet-blending process could improve the performance in co-gasification stage because of the larger pore diameter and pore volume. When anaerobic digestion (AD) time was 40 days, the synergistic interaction between digestate and lignite were the most remarkable based on the results of thermogravimetric analysis (TG) and the experiments in the lab-scale downdraft fixed bed gasifier. Kinetics study showed that the increase of AD time and the addition of digestate in lignite decreased the activation energy of the co-gasification reaction.

Silicon nanoparticles coated with nanoporous carbon as a promising anode material for lithium ion batteries

As a promising anode candidate, silicon (Si) nanoparticles have been widely studied for use in lithium ion batteries.

In Vitro and In Vivo Evaluation of Core-Shell Mesoporous Silica as a Promising Water-Insoluble Drug Delivery System: Improving the Dissolution Rate and Bioavailability of Celecoxib With Needle-Like Crystallinity

The objective of our study was to prepare mesoporous silica nanoparticles with a core-shell structure (CSMSNs) and improve the dissolution and bioavailability of celecoxib (Cxb), a water-insoluble drug, by changing its needle-like crystal form. CSMSNs are prepared by a core-shell segmentation self-assembly method. The S_BET and V_t of CSMSNs were 890.65 m²/g and 1.23 cm³/g, respectively. Cxb was incorporated into CSMSNs by the solvent evaporation method. The gastrointestinal irritancy of the CSMSNs was evaluated by a gastric mucosa irritation test. In vitro dissolution and in vivo pharmacokinetic tests were carried out to study the improvement in the dissolution behavior and oral bioavailability of Cxb. In conclusion, gastric mucosa irritation study indicated the good biocompatibility of CSMSNs. The cumulative dissolution of CSMSNs-Cxb is 86.2% within 60 min in SIF solution, which may be ascribed to the crystal form change caused by control of the nanochannel for CSMSNs. Moreover, CSMSNs could enhance the 9.9-fold AUC of Cxb. The cumulative dissolution and bioavailability of Cxb were both significantly enhanced by CSMSNs. CSMSNs with a core-shell structure are suitable as a carrier for a poorly water-soluble drug (Cxb).

One-step mild fabrication of porous core-shelled Si@TiO2 nanocomposite as high performance anode for Li-ion batteries

Nanoporous Si@TiO₂ composites with the unique core-shell architecture are conveniently fabricated through one-step selective dealloying of SiTiAl ternary alloy under mild conditions. The as-prepared composites consist of bimodal Si network skeleton as the core and interconnected TiO₂ nanosponge layer as the shell uniformly distribute on the Si surface to form the porous core-shelled structure. The nanoporous TiO₂ as the outer protective layer not only reduce the violent volume change of electrode materials for stable cycling performance but also shorten the diffusion distance of Li⁺ for high rate capacities. The inner bimodal porous Si possesses an open bicontinuous network structure that can provide the enough empty space and robust backbone to relax the volume variation of composite and guarantee the sufficient electrode-electrolyte contact area. As a result, the optimized nanoporous Si@TiO₂ composite delivers the reversible capacity of 1338.1 and 1174.4 mA h g^-1 at the current densities of 200 and 1000 mA g^-1 after continuous tests for 120 and 100 cycles, respectively. With the advantages of easy preparation, unique architecture, and high lithium storage performances, the porous core-shelled Si@TiO₂ composites demonstrate the promising application potential as an anode material for LIBs.